Formally speaking, everybody who stays in Thailand for more than 180 days a year is counted as Thai resident for tax purposes. This includes people who stay on retirement extensions visas. All foreign money brought to Thailand are taxable in Thailand if you are Thai resident for tax purposes. There was a loophole that if money stayed outside Thailand for more than 1 year, they are exempted from taxation. This loophole is now closed. It remains to be seen how expats will be treated in this situation. Double taxation treaty or not, imagine you need to bring several million baht to buy condo. How are you going to prove that it was taxed in your country in previous years? Just imagine to deal with Thai beaucrocracy...