here is what i have collected ............ it seems accurate up to a point and incomplete albeit interesting
copy paste from irs in usa all of below is copy past
1. The term "expats" refers to U.S. citizens or long-term residents who have given up their citizenship or residency to avoid U.S. taxes. In your case, since you have not formally renounced your citizenship or ended your residency, these expat tax rules do not apply to you.
you should look at Article 20, Paragraph 2, which states that:
- If social security benefits or similar public pensions are paid by the U.S. (the "Contracting State") to a resident of Thailand (the "other Contracting State") or a U.S. citizen, those payments are only taxable in the U.S.
This means that as long as you remain a U.S. citizen, your social security benefits will only be taxed in the U.S., according to the treaty between the two countries.
https://www.irs.gov/businesses/international-businesses/thailand-tax-treaty-documents
2. Notwithstanding the provisions of paragraph 1, social security benefits and other similar public
pensions paid by a Contracting State to a resident of the other Contracting State or a citizen of the
United States shall be taxable only in the first-mentioned State.