This is what I thought of doing as well. Show up in the first weeks in January with a statement from Bangkok Bank showing my 2024 transfers in Thailand. That is the easy part, I think.
The hard part, unless Thailand is using an honor system, is showing how much my USA Social Security pension is, as that portion of my income is not assessable. Is this the total amount before Medicare deductions or just the amount deposited into my bank account? So I'll take my annual SS letter with me.
My transfers are over this SS amount but less than the total SS exemption amount plus the standard Thai income tax deductions. So I should not owe any tax.
I pay taxes on all of my income in the USA and my income is only SS and private pensions. No investment income. My accountant in the USA says any tax I pay to Thailand is deductible from US taxes.