TL;DR:OTC drugs are easy to buy; carry prescriptions and original packaging. Controlled drugs need a Thai FDA permit (Form IC‑2) and have strict limits; check Thai FDA/embassy guidance before travel.
Common over‑the‑counter medicines (paracetamol, ibuprofen, antihistamines, most antacids, cough syrups) and many prescription drugs are widely available at chains like Boots and Watsons and at hospital pharmacies in major Thai cities. You should carry prescription drugs in original packaging with your doctor’s prescription or a doctor’s letter stating name, diagnosis, drug names, dosages and quantity. Non‑controlled prescription meds for personal use are normally limited to a 30‑day supply; medicines containing narcotics or psychotropic substances require a Thai FDA permit (Form IC‑2) applied for before travel (permit processing takes days and you should apply at least ~15 days before arrival) and are limited to a 90‑day supply. Category‑1 banned substances cannot be imported. Always keep the printed permit/prescription and passport when entering, and check the Thai FDA guidance and your nearest Thai embassy for your specific medicines before travel. Official sources: Thai FDA traveler guidance and Thailand embassy health pages.
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