Hemp (กัญชง) and high-THC cannabis (กัญชา) are the same plant species. The law separates them by a single lab result: how much THC the plant contains. This article covers four things. It shows where that limit sits in Thailand, the European Union and the United States. It explains what the 2025–2026 Thai rules changed and what hemp is used for. It ends with what to do at harvest so a hemp crop stays legal.
1. One species, two legal names
To a botanist, hemp and high-THC cannabis are one species: Cannabis sativa L. Both have the same leaf shape and grow the same way. Both also carry trichomes. Trichomes are the tiny resin glands on flowers and leaves where the plant makes its cannabinoids.
Cannabinoids are the plant’s active compounds. The two best known are THC (delta-9-tetrahydrocannabinol, the compound that causes the “high”) and CBD (cannabidiol, which does not cause a high).
“Hemp” and “marijuana” are not botanical groups. Regulators created the two terms to separate plants that cause little or no high from plants that cause a strong one. Many foreign laws use the word “marijuana”. This article says “high-THC cannabis” for the same thing.
In practice, hemp means cultivars bred for fibre, for seed, or for low-THC extraction such as CBD. A cultivar is a named variety selected by breeders, what most growers call a strain. High-THC cannabis means cultivars bred and selected for high THC and a psychoactive effect.
The genetics of the two groups overlap a lot. Growing conditions can change the cannabinoid profile of a single cultivar. Sometimes the change is big enough to push the plant over the legal limit. The evidence on stress is weaker than often claimed. A 2021 Cornell field trial on three high-CBD hemp cultivars (Toth et al., GCB Bioenergy) tested flooding, powdery mildew, herbicide, physical wounding and a plant growth regulator. None of these stresses raised THC or the THC-to-CBD ratio at harvest. Harvest timing matters more. In a 2020 study (Yang et al., Journal of Agricultural and Food Chemistry), THC rose as the flowers matured, and some varieties went over the US 0.3% limit in the later weeks. This is why the THC limit matters so much to growers.
What to do: Before you plant a crop as hemp, ask the seed supplier for a lab report on that cultivar’s THC level. The report tells you how far below the legal limit the cultivar normally sits.
2. The THC limit
Under most legal systems, three things do not decide whether a plant is hemp: its CBD content, its shape and its intended use. The deciding factor is one number. It is the percentage of THC that a lab measures in the dried plant material.
- Thailand: The hemp limit long used in Thai rules is 1.0% THC in the dried leaves and flowers. It was set in 2019–2020, when hemp was still regulated as a narcotic. Confirm with the licensing authority how this figure applies under the current rules. Extracts with more than 0.2% THC by weight remain Category 5 narcotics. Category 5 is one of the five narcotics categories in Thai law. Cannabis and hemp plants were removed from it on 9 June 2022. For cannabis and hemp, only these extracts remain in it. To produce, import, export, sell or possess these extracts, you need a licence under the Ministerial Regulation on Permission to Produce, Import, Export, Sell or Possess Category 5 Narcotics, Specifically Cannabis or Hemp Extracts B.E. 2569 (2026). It has been in force since 26 April 2026.
- European Union: The limit is 0.3% THC by dry weight. It was raised from 0.2% on 1 January 2023.
- United States (federal level, under the 2018 Farm Bill): The limit is 0.3% delta-9 THC by dry weight. A federal law enacted in November 2025 narrows this definition. It counts total THC, including THCA, and excludes certain products with more than 0.4 mg of total THC. Most of these changes take effect on 11 December 2026, after a one-month delay.
Translator’s note: Not everyone can get this extract licence. Licences for extracts above 0.2% THC go only to three groups. The first is Thai juristic persons (registered companies and similar legal entities) that are not “foreign” under the Foreign Business Act B.E. 2542. The others are state agencies and the Thai Red Cross Society. An individual grower or a foreign-controlled company cannot hold this licence.
Plant material that tests above these limits is legally high-THC cannabis, which is regulated more strictly. How it was grown and what it is meant for make no difference.
CBD does not decide the category either. A plant can be very high in CBD and still count as high-THC cannabis if its THC is over the limit. That is why a lab test at harvest is essential if your crop grows close to the limit. The lab issues a Certificate of Analysis (COA), a report that lists the cannabinoid levels found in your sample.
Translator’s note: Thailand’s 1.0% limit for plants is higher than the 0.3% used in the EU and the US. That gives you some margin if you grow a cultivar registered abroad as hemp. However, that 0.3% result was measured in a different climate. Keep in mind too that a plant can be legal hemp and still give an illegal extract. Extraction concentrates cannabinoids, so a plant below 1.0% THC can produce an extract far above 0.2%.
Translator’s note on timing: Test twice. Send the first sample in late flowering, while there is still time to plan. Send the second from the harvested, dried batch. That second result is the one that shows the legal status of what you sell.
What to do: Send a sample of every batch you plan to sell or process as hemp to a lab before it leaves your farm. File the COA with that batch’s records. This shows you whether the batch is legally hemp, and it gives you proof if an inspector asks. Choose a laboratory accredited to ISO/IEC 17025 for cannabinoid testing, and ask to see its accreditation scope. You can also ask other members about their lab experience in the B2B Services section (laboratories).
3. Thailand’s rules in 2025–2026
The main change came from the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568. It was issued under the Thai Traditional Medicine Protection Act B.E. 2542 and came into force on 26 June 2025. Cannabis flower (ช่อดอกกัญชา) is now a controlled herb. It is no longer a fully open farm product. The main points:
- Two newer regulations add the detail. The Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569 has been in force since 26 April 2026. The Ministerial Regulation on Controlled Herbs (No. 2) B.E. 2569 came into force on 30 April 2026. It tightens the licence criteria for cannabis flower. Together, these two regulations set licensing and sales conditions for cannabis and hemp businesses.
- PT 33 (ภ.ท. 33) is a prescription form, not a permit. A licensed practitioner writes a PT 33 prescription covering no more than 30 days. Only then may flower be dispensed to the patient. Growing, processing and selling each need their own licence. None of them depends on a “PT 33-exempt threshold”, because no such threshold exists.
- Hemp: Hemp plants are not narcotics in Thailand, but hemp extracts above 0.2% THC are. Whether growing, processing or selling hemp flower needs a permit, registration or traceability records depends on the activity. Confirm it in writing with the licensing authority before you start. Traceability means records that show where each batch came from and where it went.
- Flower may be sold only for medical use, on a PT 33 prescription. Selling it for recreational use is not allowed. Advertising cannabis flower and selling it online are also banned. See the advertising and selling rules for what you may post on this forum. Medical use and industrial hemp remain the main legal areas for growth.
Translator’s note: Section 78 of the 1999 Act provides penalties of up to 1 year in prison, a fine of up to 20,000 baht, or both. The draft Cannabis Control Act is not law yet. The Cabinet approved the draft on 22 September 2026 and sent it to the House of Representatives. The rules above may change again if it passes.
What to do: Before you expand any growing operation, take three steps.
- Confirm in writing which licence each of your activities needs: growing, processing, selling. This stops you from running an activity your licence does not cover.
- Keep every lab result, organised by batch. These records show inspectors and buyers that each batch was within the limit.
- Check that your registration is current. An expired registration can make a legal crop unsellable.
PT 33 matters only if you dispense flower to patients. It is not something a grower applies for.
4. What industrial hemp is used for
Hemp is fibrous, grows fast and is low in THC. That gives it many uses beyond cannabinoid extraction.
4.1 Fibre and textiles
Bast fibre comes from the outer layer of the stalk. It is long and strong. It is used for rope and canvas. It is used more and more for sustainable clothing and technical textiles, which are fabrics made for a function such as industrial use.
4.2 Hempcrete for building
Hurd is the woody core of the stalk. Mixing hurd with lime and water makes hempcrete, a light building material that lets moisture pass through. The original article calls it carbon-negative, meaning it stores more carbon than is released in making it. It is used for insulation and for walls that do not carry the building’s weight.
4.3 Car parts
Several carmakers use hemp-fibre composites for door panels, dashboards and interior trim.
4.4 Food: seeds and oil
Hemp seeds contain all nine essential amino acids, although lysine is the limiting one. They are rich in omega-3 and omega-6 fatty acids. Cold-pressed hemp seed oil goes into cooking, food supplements and cosmetics. Translator’s note: hemp seed oil is pressed from the seeds and is not the same as CBD oil.
4.5 Bioplastics
Cellulose from hemp can be processed into biodegradable plastics. These are a renewable alternative to petroleum plastics for packaging and consumer goods.
Translator’s note: Hemp is not new to Thailand. Hmong communities in the northern highlands have long grown hemp and hand-woven its fibre into traditional cloth. Industrial-scale processing is a separate question, so check what exists near you. Hemp stalks are bulky and expensive to transport. A field with no processor nearby can leave you with a crop you cannot sell.
What to do: Before you plant hemp for fibre or seed, find a processor or buyer and agree on the quality they need. Then grow a small trial plot first. The trial shows you the real yield and costs before you commit a whole field.
5. Hemp and high-THC cannabis compared
| Factor | Hemp | High-THC cannabis |
|---|---|---|
| THC content | Under 1.0% in the plant; under 0.2% in extracts (Thailand) | Typically 5%–30% or more |
| CBD content | Often high | Varies; often low compared with THC |
| Main use | Fibre, food, building materials, bioplastics, CBD wellness products | Medical use and psychoactive effect (sale for recreational use is not allowed in Thailand) |
| Causes a high | No, or very slight | Yes |
| Legal status in Thailand | Not a narcotic as a plant; extracts above 0.2% THC need a licence; confirm permit and registration needs for your activity | Controlled herb; flower dispensed only on a PT 33 prescription (max. 30 days) |
| Bred for | Stalk and seed yield, fibre quality | Cannabinoid and resin production |
6. Why this matters for growers
If you grow in Thailand, the hemp line has direct consequences. It decides which licence applies and what paperwork you need. It also decides whether you can legally sell the harvest at all. A crop grown as hemp that tests above 1.0% THC by dry weight at harvest is no longer hemp in law.
The original article gives three causes. The first is genetic drift, meaning a cultivar’s traits slowly change over generations. The second is environmental stress, and the third is late harvest. The evidence is strongest for harvest timing. In the 2020 study cited above, THC kept rising as the flowers matured. The 2021 Cornell trial found that the stresses it tested did not raise THC, and pointed to genetics instead.
Knowing where the line is lets you do three things. You can choose stable, tested genetics. You can follow THC levels through flowering. You can time the harvest correctly. This protects your legal status and keeps the business running. The 2568 Notification and the two 2569 Ministerial Regulations are now fully in force. Every grower, processor and seller in Thailand needs to keep up with registration, licence conditions and testing rules.
Translator’s note: Thai conditions add stresses that temperate growers rarely face. Hot-season rooms often reach 30–35 °C, the rainy season brings high humidity, and power cuts interrupt indoor light and air conditioning. A cultivar that stays under the limit abroad is not guaranteed to do the same here, so test it in your own conditions. Seeds or clones from unverified sources add more risk. You can end up with the wrong cultivar, with THC well above what the label says. Clones bought from other farms can also bring pests and hop latent viroid (HLVd), a disease that weakens plants.
Translator’s note: If a hemp batch tests above 1.0%, stop. Do not sell it or move it as hemp. Ask a second lab to test a new sample from the same batch to confirm the result. Then contact the licensing authority before you do anything else with the batch.
What to do this season:
- Get a lab report on THC for every new cultivar before planting, so you know its margin below 1.0%.
- Grow the first run of a new cultivar as a small batch and test it, to see how it behaves in your own heat and humidity.
- Test in late flowering and again on the dried batch. The first result gives you time to act, and the second proves the batch’s status.
- Keep the COA, seed source and harvest date together for each batch, so you can show inspectors and buyers the full record.
- Recheck your licence and registration before you expand.
Do you have questions about testing, licences or how your cultivars perform in Thai conditions? Post them below this topic so other growers can share their experience.
References
- Ministry of Public Health, Thailand — Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568
- Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569 — in force 26 April 2026
- Ministerial Regulation on the Permission for Study, Research, or Export of Controlled Herbs, or Sale, or Processing of Controlled Herbs for Commercial Purposes (No. 2) B.E. 2569 — in force 30 April 2026
- WHO Expert Committee on Drug Dependence, 41st meeting (Geneva, November 2018) — critical review reports: Cannabis plant and resin; Extracts and tinctures of cannabis; Delta-9-tetrahydrocannabinol; Isomers of THC
- U.S. Agriculture Improvement Act of 2018 (Farm Bill) — hemp definition, 0.3% delta-9 THC limit; definition amended by federal legislation of November 2025 (most changes effective 11 December 2026)
- European Union — EU Common Agricultural Policy, industrial hemp THC limit (0.3% since 1 January 2023)
- Asiannabis Community — discussions in the Safety and Regulation category