I'm going by the lowest tax rate. Up to 150k no tax, after 150-300 is 5%. Easily offset by tax paid overseas. Agree bringing cash into Thailand is a remittance, but totally untraceable.
Realistically anyone on a DTV (where there is no necessity to transfer money into Thailand) can easily avoid any taxation in Thailand, simply by transferring 300,000 through a bank, and bringing any other money in cash. Cash is the only way to avoid tracking
I don't know which country you're from and perhaps Thai education standards are higher than in your country. However, I personally would never attempt to educate my children in Thailand. Unfortunately, price paid has absolutely nothing to do with the quality of education.