If you have a foreign license already, it is quite easy to obtain a Thai license. This is what you will need:
If you are going to do a motorcycle license too, you will need to make another copy of all your documents as well.
Initially you will get a 1 year “temporary”, then you will have to come back to renew with the same paperwork again and the fee will be 605 THB for the 5 years card.
If you do not have a foreign license or it is expired, in addition to the paperwork above, you need to be there at about 8:30 to sit through a 4 hour training course (in Thai so take a translator if you want), then take the written (English available) and driving tests (you need to provide your own vehicle). Be prepared for a full day event.