Anonymous participant 600 you can not like him but it is the revenue officials telling you what they demand.. If you have a higher source than the revenue department for revenue issues then please show it.
Anonymous participant 600 even if your income is dta protected, and over many dta's it would not be, you still need to file, present the overseas tax bill and receipt to show you paid it, calculate the Thai tax bill (often higher) then tax paid overseas is deducted from tax due here.
That may mean nothing is due here, but legally you must still file and prove nothing is due here, it's not on the honor system.
I am a cross border payroll and tax professional. This is my day to day profession.