Do you even need a special visa?
Most short medical trips to Thailand — a health screening, a single dental visit, a consultation — don't require anything beyond the standard tourist entry available to citizens of many countries, which typically allows a stay of 30 to 60 days depending on nationality.
The Medical Treatment (Non-Immigrant "M") visa
For longer or multi-stage treatment — IVF cycles, bariatric surgery follow-up, multi-visit implant work — Thailand offers a Medical Treatment visa (Non-Immigrant Category "M"), which allows longer stays and can be extended in-country with a letter from your treating hospital confirming an ongoing treatment plan.
To apply, you'll generally need: a passport valid for at least six months, a letter of acceptance or appointment confirmation from a Thai hospital, proof of funds, and — depending on your embassy — a medical certificate. Requirements vary by Thai consulate, so always confirm the current list directly with the consulate covering your country before applying.
Practical tips
One practical tip: ask your coordinator for the treatment confirmation letter as early as possible in the process. Many consulates require it as a supporting document, and hospitals typically need a few business days to issue it once your treatment date is confirmed.
If your treatment plan changes while you're in Thailand — for example, your recovery takes longer than expected — a licensed immigration agent or the hospital's international patient office can usually help arrange a visa extension without requiring you to leave the country.