Is Heroin legal in Thailand?

Also known as: diacetylmorphine, smack

Legal status

Heroin is a Category I narcotic in Thailand. The Thai FDA table of controlled narcotic drugs updated 15 September 2025 prints the heading ยาเสพติดให้โทษประเภท 1, narcotics subject to penalty of category 1, and carries heroin as an entry beneath it. Heroin sits in Category I while morphine and opium sit in Category II in the same table, so the opiate family is split across two categories and two penalty sections. The placement is not written into the Narcotics Code B.E. 2564 itself: section 90 leaves the names and the categories to Ministry of Public Health notification, and the FDA table is the consolidated republication of those notifications, read here through its last Category V entry. So the Code supplies the offence and the penalty while a notification supplies the identity, which is also why this status can move without the statute changing.

Consequences if caught

Capital exposure: only through section 145 paragraph 3, and only on that paragraph's own conditions. It is the narrow top of that section rather than the ordinary case: paragraph 3 permits 5 years to life plus a fine, or death, only where the actor leads or manages a criminal network or the conduct affects state security or public safety, so the death alternative is discretionary and circumstance based and no stated weight of Heroin triggers it. Ordinary conduct falls under section 145 paragraph 1, which allows up to 15 years. A traveller holding a personal quantity is in paragraph 1 territory and not in paragraph 3 territory. Paragraph 2 reaches 2 to 20 years for commerce, public dissemination and the listed aggravators. Nothing in that structure makes a quantity the switch between the limbs, which is the single point English summaries of Thai drug law most often get backwards. Morphine and opium sit in Category II in this same table under section 146, so the opiate family is split across two penalty sections and this row is on the heavier one.

If prescribed or medical

Heroin sits in narcotics Category I on the 15 September 2025 table, and that criminal classification is the whole of what this dossier settles about a person holding it. Thailand's country level traveller rule for personal medication was not established by this reading. The sources opened were the Narcotics Code B.E. 2564, the Thai FDA narcotics table updated 15 September 2025 and the B.E. 2565 psychotropic naming notices in the Royal Gazette, and the dossier is explicit that its findings come from those naming instruments and not from a traveller permit label, so no import permit route, no personal supply quantity ceiling and no certificate requirement can be stated here for Heroin. What is missing from this row is the permission, not the classification, and the gap is in what was read rather than a finding that no lawful route exists. No medical route is in question here, and the split from morphine is what makes this row's exposure unlike the rest of the opiates this table answers.

Documentation

Carry the finding with its date attached rather than a document this row can vouch for: Heroin was read in Category I of the Thai FDA table of controlled narcotic drugs updated 15 September 2025, and no Thai permit, exemption or traveller allowance answering that placement was established here. Check which opiate is named, because this table places heroin under section 145 and morphine and opium under section 146. The reading was taken on 20 September 2026 from the consolidated narcotics table, at https://narcotic.fda.moph.go.th/media.php?id=808160206197497856&name=NARCO+list+(update+15.09.2025)+NEW.pdf. No express open reuse licence was located on the cited page, so only the wording needed for verification is reproduced, with attribution and a direct link. The names and categories are set by ministerial notification, and the publications do not certify that no later notification exists, so re-read before relying on this.

Drug laws and enforcement change and vary within a country. This is not legal advice. Always confirm with Thailand’s embassy or official drug authority before traveling; penalties can be severe, including imprisonment.