@Koj***
I got my licenses through the Department of Land Transport (DLT) offices in Udon Thani and Khon Kaen. The process is pretty straightforward if you're proactive. Just check the DLT website or visit your local office to find out the requirements. I managed to do it myself at a provincial office without knowing any Thai, so it's definitely doable.
Even if you're not in a rush because you have an international license, it's still worth sorting out. Since you have an LTR visa, you'll need one eventually for local life.