Close. If you get a positive rat you ate required to take a pcr at your own expense to confirm the result. When that comes back you are required to self isolate somewhere suitable if you cant you will be required to isolate, again at your own expense, at a suitable government location
All this is quite easily found on the Thai govt ministry of health website.
Of course rhis is what you are officially supposed to do. What actually happens is up to the individual in question.