Duty-free allowances, restricted items, and what travellers frequently get caught with.
200 cigarettes or 250g tobacco; 1 litre of wine or spirits; personal effects of reasonable quantity — standard international allowances.
Firearms require a permit (strictly enforced); some medications (codeine, certain painkillers) require a doctor's letter; drone registration required.
Vaping devices and e-cigarettes are illegal in Thailand — confiscation and significant fines; don't risk bringing them.
No limit on foreign currency but amounts over 450,000 THB equivalent must be declared on arrival; amounts over 50,000 THB must be declared on departure.
All arrivals complete a customs declaration form; declare honestly; random bag checks do occur; the penalties for undeclared goods are significant.
Prescription medications should travel with their original packaging and, ideally, a doctor's note; commercial quantities of anything (even souvenirs) can trigger extra scrutiny at customs.
Thai Customs Department's official website has the current, authoritative list of restricted and prohibited items — worth checking directly if bringing anything unusual.