I've been saying I'd get a Thai car/motorcycle driving license for about four years now, but just had never gotten around to it. After years of experiences with US Department of Motor Vehicle (DMV) offices, I wasn't exactly in a hurry to deal with what I expected would be an even worse experience. Luckily for me, I was wrong!
Take a Thai
I went to the "main" Bangkok office just next to Mo Chit BTS. I was especially surprised that the majority of stuff I needed to do/watch was available in English (or almost-English) soundtrack (for how-to videos) and/or subtitles (for the required hour-long safety video, consisting primarily of some hot Thai movie star named Manow... I've seen worse).
That said, almost none of the paperwork was in English, and few of the staff I encountered spoke enough English to ask any real questions, so I'd highly (highly) recommend taking someone Thai with you to avoid frustration.
I won't go into huge details about what to do to get the license, but will suggest you check out this webpage for a fairly detailed and up-to-date (as of July 2016) process of what you need, and here for a link containing *literally* 85% of the current motorcycle license "exam" questions, which are surprisingly available in English (but only just). You'll also want to make sure you have 2 copies of everything important from your passport AND work permit (it seems to be a no-go without a work permit), and your current foreign license; just take those to the copy lady just inside the building and she'll know exactly what you need.
Note that the work permit serves as your required "residency certificate," and you do NOT have to get one of those from your embassy or Thai immigration.
If you have a US license (and I assume most European countries, but don't know for sure), you can bypass the "written" driving exam and practical driving test, which I understand requires you make an appointment at the time of application (in person, not over the phone), and return a month or so later due to backlog. You'll only have to do the color/reflexes tests (for car and motorcycle licenses), which are a piece of pie and/or joke; just copy what the Thais do and you'll be fine.
In Thailand, though, you get a separate motorcycle/car license with different numbers, so I opted to kill two birds with one stone and get both the same day. My US license didn't cover motorcycles, so I had to do the 50-question computerized exam and practical driving test; for the exam, I *highly* recommend reviewing the questions (link above), as, with this being Thailand, you can't simply "logic" your way through the exam, and you must get 45/50 to pass; they're looking for specific (often random) answers, and when you see the questions above you'll understand what I mean. I never would have passed without reviewing the questions/answers just before the exam. (Apparently, it IS legal to drive a tank through Bangkok...)
On two wheels
For the motorcycle driving test, there really wasn't much to it; the hardest part was driving across a narrow raised platform for 10 seconds without falling off, but ironically enough, of the four of us taking the test, I, the foreigner, was the only one to pass the first time; all of the Thais apparently missed the last stop sign. Just pay attention, heed the stop signs, and you'll be golden. I will note that the motorcycle you can rent there (50 baht, automatic) is OLD and doesn't exactly handle nicely.
All in all, though, I arrived just after 8:00, and was out of there by about 12:30, which considering my experiences with the Georgia DMV in the US, is a walk in the park. The majority of the staff there were nothing but smiles, and aside from having to go through the usual bureaucratic BS, it was surprisingly painless. I now have two licenses for 510 baht total, shiny and all, that are valid for two years; apparently I can renew them both for five years just after they expire with just another eye/color/reflex test and payment.
If nothing else, they'll make nice good luck medallions to hang in the secondhand car I'm about to buy.
I hope you enjoyed my blog. If you would like to get in touch or perhaps e-mail me with a question, I would love to hear from you - All the best, Sam Thompson.