the last bit of advice I would give you is don’t go looking for a place to rent or buy on Facebook. And don’t post what your budget is. Try and get a Thai person to check for you so you get the best deal. I see a lot of foreigners, getting raped and paying double what they should for a rental. Your best bet is to drive around and look at for rent or for sale signs. Put in the work and save thousands of dollars. 
get an international drivers license in the states so you can convert it to a Thai drivers license without having to take the test. You’ll just have to take the eye test and reaction test.
yeah that answered his question about taxes. Maybe you should recommend a good taxi service to pick him up for a tour of the Grand Palace as well…🤦♂️
funny I have been living here since 99 and haven’t seen that. You must have some inside sources, but I doubt it’s true. I’ve flown in and out of Bangkok hundreds of times and never been flagged. I just walk through like I own a place.