How much documentation is needed for a 90 day medical extension?
Would there be a huge difference in where the paperwork comes from, when it comes to it being a success or not?
Really need some treatment that will take some time, would prefer to do that in Thailand rather than being thrown out...
TLDR : Answer Summary
The documentation needed for a 90-day medical extension in Thailand depends on the discretion of the immigration office and the specifics of the doctor's letter that requests the extension based on medical necessity. If you are able to travel, it may result in a denial of the extension, so it's crucial to consult with your doctor about the situation.