You do nothing. There are fear mongers out there who actually believe Thailand will tax savings. They cannot get it into their thick heads it's only possible to tax UNTAXED INCOME.
Genuine feedback? What do expect to pay for a guaranteed five year visa? You really believe a cooking course will cost that much in Thailand? Still, I see you are choosing to live in that Godforsaken wilderness called Isaan. That speaks volumes! π
It's perfectly legal for you to have two passports, even from the same country. You use the one with the Thai visa to enter and leave Thailand, and the other one to show when checking in for your flight