I used an agent, there is a lot of faffing around to get one, 1) make appointment at test center, 2) make appointment at license office 3) take the test which is a colour sight and reaction test 4) get medical certificate 5) get all your papers together, like visa, residence cert 6) take it the license center and wait around. Hence use an agent.
Thailand does discriminate against people who enter and stay in the country legally and those that don't. Hence, I am a racist a homophobe, islamophobias and antisemite.