No. You are obligated to fill in a tax return listing the money you bring into Thailand. And then producing evidence to show what tax you have already paid in other countries. That may or may not leave you with a tax liability in Thailand.
Everything up to here is fact already. Here is where I'll speculate. Thai authorities will become concerned at the level of both ignorance and tax evasion on the part of foreign residents. The government will then instruct Immigration to seek evidence of tax returns filed when foreigners apply for an extension of stay
Read in official sites what the Thai Revenue leaders have said and stop spreading misinformation. I won't give you the links or you'd just accuse me of wanting clicks. Seek it out for yourself
Thailand is considering taxing the global income of those who spend more than 180 days here in any year. But right now the law is interested only in money you bring in to Thailand wherever it is earned. It doesn't matter whether the money is salary, pension, investment income, capital gains ... if you bring money to Thailand and stay 180 days, that money is assessable for Thai income tax. That said, tax already paid in another country will off-set tax assessed here, if that country has an DTA with Thailand
