USA messed up, Trumpers don’t even want tourists, any sort of illegal entrant has a chance to stay, and no provision for an American to be a guarantor except marriage. My friend has several full passports with stamps from many Schengen and other non 5-eyes countries.
You can attend any kind of school in Thailand on any valid visa. But, some people get an education visa, and go to a school, as a way to stay in Thailand for a while.