Is an International Driving License required for extending an existing Thai driver's license?

@Radost *************************

guess what. Immigration requirements are also written into law but every immigration office has their own requirements. The MFA has visa requirements written into law but every embassy has their own requirements. If you don't know how Thailand works then don't post. You only have to be in these forums for a few weeks to see different requirements at different offices. The DLTs don't even consistently test for foreign license conversions or license renewal with some doing and it and some not.

How on earth did you get not meeting requirements with "check with the DLT you will be using"? Nothing about corruption, it's about making sure you have everything that specific office requires. Because they are NOT all the same.

@Brandon ***********

there are no test upon renewing a license, there is a requirement to watch a video in english language and a reaction test. You can change requirements, if you could they could change the age, the kind of idk, the price, or whatever. I guess you never solved any problem at a government office. I am 11 years in Chiang Mai and I got what I needed and sometimes I got even more.