The OP mentioned a potential new risk of high taxation in Thailand based on proposals to tax worldwide income - I agreed that it would likely cause many people to leave, at least to the point of becoming non tax resident in Thailand.
Of course they'll be subject to tax rules elsewhere, no one has suggested they wouldn't. Regarding DTAs etc, the Revenue Department has failed to make things clear at the present time, especially regarding what constitutes assessible income etc. But that's a different topic completely.