My advice would be to not do any building until you're in Thailand. But before you even think about that you need to employ a Thai architect to produce the full set of architectural drawings which have to be signed off by the local Or Bor Thor office to get a building permit. Don't build something from a rough plan. I paid a Thai architect 10,000 baht to produce my drawings. Only then did I think about construction.
immigration doesn't know if you stay in an apartment for 3 days before returning to your registered address. They haven't implanted a tracking chip inside you. 😄