Agree with above posts regarding original licence needed. I got both my Thai car and bike licences before Christmas in Chiang Mai. Easy enough. My requirement list was.
Passport, Visa, Original licence, IDP, Cert of Res ( as CM involves 2 trips to immi and I am only on a Tourist Visa I used an agent. Tell them it is for a driving licence as the reason is written on the Cert of Res) Medical Cert (mine was 30B and completed by receptionist!) Photocopies of just about everything.
Some of the above may not be required but it is what I took.
At DLT colour blindness test and 40 min video. I had to hang around to watch the video as I hadn't booked a slot on line. Still done and dusted same day and walked out with both licences. 105B each from memory. Good luck.