Actually my $100 monthly possible tax bill -- using only current deductions no US-Thai DTA Article 20 -- may be even less as I will have a 60,000 baht annual deduction for life insurance premium paid to a Thai Life insurer.
Again from the US Embassy Bangkok website:
"The Economic Section monitors economic, financial, energy, trade, investment, and labor trends in Thailand. The team presents U.S. views on bilateral and multilateral economic issues to the Thai government and the public."
So they may have something to say if it turns out that each Thai provincial RD office is allowed their own interpretation of the US-Thailand DTA.
https://th.usembassy.gov/embassy-consulate/bangkok/sections-offices/economic-section