What Is Cannabis? The Plant, THC and CBD, Hemp Versus Cannabis, and the Thai Rules Growers Need to Know

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Cannabis is the plant Cannabis sativa L. and the products made from it. People value it mainly for its cannabinoids, a group of related plant compounds. The best known is THC, which causes the intoxicating “high”. The second is CBD, which does not intoxicate in the same way.

Law decides whether a plant counts as “hemp” or “cannabis”, based on how much THC it contains. Botany does not draw that line. In Thailand, cannabis flower is currently a controlled herb. The public can buy it only with a prescription. This page explains the plant and the rules. It does not point anyone to a shop.

The plant

The World Health Organization (WHO) uses “cannabis” as an umbrella word for the psychoactive preparations made from Cannabis sativa. Psychoactive means the preparation changes how the brain works, for example mood or perception. WHO names delta-9-tetrahydrocannabinol (THC) as the main psychoactive compound. Substances with a chemical structure similar to THC are grouped together as cannabinoids.

Seed packets and menus often use the labels indica, sativa or ruderalis. These labels describe types within one species. They are not separate species. All of them are Cannabis sativa L., a member of the plant family Cannabaceae.

Cannabis is usually grown for its female flowers. A plant-science review from McGill University in Canada explains where cannabinoids are made. They form in stalked glandular trichomes, which are tiny resin glands on short stalks. These glands crowd the surface of the female flowers.

The same resin also carries terpenes, the compounds behind the smell. It also carries flavonoids, a group of plant compounds that includes many pigments. This is why the flower matters most, both for medicine and for the law.

Translator’s note: When you send a sample to a laboratory, send flower, not leaf or stem. Cannabinoids are made in the flower’s resin glands. A flower sample therefore shows what the law and your buyer will actually measure.

The main compounds, and why fresh flower tests differently

The living plant makes mostly the acid forms of these compounds. These are THCA (tetrahydrocannabinolic acid) and CBDA (cannabidiolic acid). The McGill review notes that fresh flower contains relatively little THC and CBD. It contains much more THCA and CBDA.

The acids turn into THC and CBD through decarboxylation. In this chemical change, the acid form loses a small part of its molecule and becomes the non-acid form (also called the “neutral” form). It happens during post-harvest handling and storage. Temperature and light are the main drivers.

This has two practical results. A laboratory report, called a certificate of analysis, lists both the acid forms and the non-acid forms. Heat also matters in any preparation, because heat is what turns THCA into THC.

Compound What it is Key point
THCA Acid form made in the resin glands Turns into THC with heat and time
THC Main psychoactive cannabinoid The figure used to draw the legal line for hemp
CBDA Acid form of CBD Turns into CBD with heat and time
CBD (cannabidiol) Cannabinoid that does not intoxicate in the same way Purified CBD is the active ingredient of an approved epilepsy medicine

Translator’s note: Store rooms in Thailand often sit at 30–35 °C. Heat and light drive the change from THCA to THC, so warm flower kept in the light keeps changing after harvest. A test at harvest and a test after storage may then show different THC figures for the same batch. Keep dried flower in a dark, cool place (see storage). Write down the harvest date, storage date and room temperature for each batch. Add these details when you send a sample. With these records you can explain why two reports on one batch do not match.

Hemp versus cannabis: a line set by law

Hemp and drug-type cannabis are the same species. A THC limit written into law is what separates them. Each country or region sets its own limit:

  • European Union: hemp grown with farm support must be a variety with a THC content below 0.3%. It must be grown from certified seed of varieties listed in the official catalogue.
  • United States: federal law defines hemp as Cannabis sativa L. with a delta-9 THC concentration of not more than 0.3 percent on a dry weight basis. “Dry weight basis” means the figure is calculated on the sample after its water is removed. From 12 November 2026, an amendment (Public Law 119-37, section 781) changes this to a total THC concentration, including THCA, of not more than 0.3 percent on a dry weight basis.
  • Thailand: the plant came off the narcotics list in 2022 (see Thailand’s cannabis rules, 2022 to 2026). At that time, extracts with more than 0.2% THC stayed classified as narcotics. The current controlled-herb notification covers plants of the genus Cannabis, family Cannabaceae, and does not name hemp separately. Only the flower is a controlled herb.

A crop called “hemp” in one country can therefore be “cannabis” in another. A product that is legal where it was made is not automatically legal where you live.

Translator’s note: Hemp is defined by a maximum THC level, not by zero THC. If you grow a variety sold as “hemp”, test a flower sample from your own batch before you sell or ship it. The test tells you whether the batch is under the limit that your buyer’s market uses, for example 0.3% for buyers in the EU or the US. Ask the laboratory and the buyer which figure counts: THC alone, or a total that also includes THCA. In the US, the USDA hemp testing rules already use “total THC”, which includes THCA. From 12 November 2026 the federal definition of hemp also counts total THC, including THCA. Start with one sample per batch. Keep each report with that batch’s records.

Translator’s note: In Thailand, treat the word “hemp” on a seed packet as a description of the variety, not as a legal status. The current notification covers all plants of the genus Cannabis and does not name hemp separately. Before you plant, find out which rules apply to your crop. Do not rely on the packet label alone.

Which parts are used for what

  • Female flowers (the flower clusters, called inflorescences): the main source of cannabinoids and terpenes. They are used for medicinal preparations and for extraction.
  • Stems and stalks: used for fibre and for the woody inner core of the stem. The European Commission describes hemp fibre as very similar to linen. It also reports growing interest from the textile industry.
  • Seeds: used as food, including animal feed. Seeds are also grown for sowing, under the variety rules above.
  • Leaves: in Thailand, the current notification makes only the flower a controlled herb. Leaves and stems are not controlled herbs under it.

Translator’s note: Only the flower is controlled in Thailand. At harvest, keep flower apart from leaves and stems, and label each container. Then your records show which material falls under the controlled-herb rules. If you plan to sell seed as food, first read the linked topic on hemp seed and Thai food law.

Cannabis in Thailand today

The rule that matters most is 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 (1999) and has been in force since 26 June 2025. It keeps cannabis flower as a controlled herb. It also allows retail sales only on prescription:

  • A member of the public may buy flower only with a prescription on the official form PT 33 (ภ.ท.33). The prescription must come from an authorised practitioner and may cover no more than 30 days.
  • Sales through websites, social media, vending machines and other electronic channels are prohibited. Advertising cannabis flower through any commercial channel is also banned.
  • Flower may not be sold in places such as temples, dormitories and public parks. It may not be sold for smoking on the premises, unless an authorised practitioner uses it as part of treatment.

Extracts fall under a separate rule, the Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569. It has been in force since 26 April 2026.

Translator’s note: Under the extracts regulation, licences for extracts with more than 0.2% THC go only to three groups. These are Thai juristic persons that are not “foreign” under the Foreign Business Act B.E. 2542, state agencies, and the Thai Red Cross Society. A second rule, 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.

Translator’s note: Section 46 of the 1999 Act requires a licence to research, export, sell or process a controlled herb. Doing any of these without a licence carries a penalty under Section 78: up to 1 year in prison, a fine of up to 20,000 baht, or both. For growing itself, confirm which rules apply to your farm before you plant. Before you sell flower or biomass (harvested plant material) to anyone, confirm that you hold the right licence. Also confirm that the buyer holds theirs, and keep copies of both. If an inspector asks, these copies show that every sale was legal on both sides.

On 22 September 2026, the Cabinet approved the draft Cannabis Control Act and sent it to the House of Representatives. The draft was earlier called the Cannabis and Hemp Act. It is not law yet. Its stated aim is to limit cannabis use to medical purposes.

This page does not list or recommend shops. If you are looking for a “cannabis shop near me” in Thailand, the legal starting point is a medical consultation, not a storefront.

Translator’s note: If you live elsewhere in Southeast Asia, Thai rules do not apply in your country. Cannabis remains illegal in several countries in the region. Read the country summary in Cannabis Laws Across Asia, Part 1 before you grow, buy or carry anything.

Health risks are part of the picture

WHO lists harms linked with regular use. They include impaired attention and memory. Chronic users are also likely to develop a dependence syndrome, meaning they lose control over their use. WHO also notes that cannabis use can worsen schizophrenia in people who already have it. Read this part as carefully as the sections on the plant and the law.

Translator’s note: If people on your farm or in your household use cannabis regularly, share these WHO points with them. If someone notices they can no longer control their use, they should see a doctor.

Common mistakes

  • Treating indica and sativa as different species. They are labels for types within Cannabis sativa L.
  • Assuming hemp means zero THC. Hemp is defined by a maximum level (0.3% in the EU and the US), not by the absence of THC.
  • Reading a THC figure without checking the form. Fresh or raw material is mostly THCA, which turns into THC with heat. Check whether a report shows THC, THCA, or both.
  • Assuming Thai shops can sell flower to anyone. Since June 2025, members of the public need a prescription to buy flower.
  • Assuming a Thai purchase can travel with you. Thai authorities urge travellers to check the law of their destination, because cannabis is still a serious illegal drug in several countries (see rules for visitors to Thailand).

Before you act

Thai rules have changed several times since 2022, and the new bill is still before the House of Representatives. Before you act on anything here, read the current notification and your own country’s law. The topic Read the Original Legal Texts explains where to find the Thai texts. Note the date you checked, so you know when to check again.

If you have a question about your own crop, your test results or your local rules, post it below this topic so other growers can answer.

References

Cannabis Laws Across Asia and Key Global Markets, 2026: Thailand and Southeast Asia (Part 1 of 2)
Thailand's Food Advertising Criteria B.E. 2569: What Changed on 28 July 2026 for Cannabis, Hemp and Kratom Foods and Drinks
How the United States Banned Industrial Hemp in 1937: The Tax Law, the State Laws Before It and the Doctors Who Objected (Part 1 of 2)
Hemp and the Wars of 1812: What Is True About Napoleon and Russian Rope, and What Is Myth
Thailand's Cannabis Rules, 2022 to 2026: From the Narcotics List to Controlled Herb (Part 1 of 2)
Cannabis and Hemp Flower Export from Thailand, a Working Glossary: Plant Parts, THC Figures and Thai Legal Terms (Part 1 of 2)
Cannabis Laws Across Asia and Key Global Markets, 2026: East Asia, South Asia, Israel and Europe (Part 2 of 2)
Advertising and Selling Rules for Cannabis in Thailand: What You Can and Cannot Post on Asiannabis (Part 1 of 2)