Under the old system of entry and exit stamps, I filled up my passport in 5 years. Hopefully, my current passport will last the full ten years by saving Thai exit stamps, entry and exit in Malaysia and Singapore, and stampless entry and exit in Macao and Hong Kong.
Thailand cannot legally rewrite the DTA with the US, as it's a bilateral treaty.
But your understanding of the tax consequences of the DTA are not accurate.
For example, the US gets first crack at taxation of Social Security and other income streams generated in the US, but then if Thailand's marginal tax rates are higher, Thailand would tax the income streams at its tax rates, minus whatever was paid to the US. The DTA only provides for coordination of taxation between the two countries.
If you are a US citizen and a Thai tax resident, you are going to pay the same tax amount in total (to the two countries ) that you would pay Thailand if you weren't a US citizen.