I suggest you take your passport and all other documents you can imagine pertains to driving licenses. Go to the DLT office and ask them what you need to do. They are probably most helpful. At least they are in Chiang Mai.
Then you’ll get it from the horse’s mouth.
When I got my licenses (2007) I could not use my Norwegian license as it is not in English. I had no desire to travel to Bangkok for a translation, so the lady suggested I take the test. I went back the next and by 3 pm I had both licenses. The test is ridiculously easy.