@Gabriel *******
you're talking as if only three countries have a tax treaty with Thailand, but I'd be surprised if you can find even one the doesn't.
The big change of the new tax system is when you owed tax in Thailand based on the 180 days rule, and not elsewhere based on similar rules there, but then owed 0 because you didn't remit your income. Then you now pay tax, as, let's be fair, you should. But then you already stayed here for 180 days before the changes.
If you didn't stay here 180 days and now do, odds are you you owe less tax than before. Being taxable in Thailand is not something I'd particularly prevent, I'd actually rather aim for it. The taxes are a laugh.