@William *****
far too big a list of questions for here but very basically it is income that you bring in to Thailand that is taxed, it doesn't matter how you bring it in. Whether or not your income is taxable in Thailand is determined by the Dual Tax Agreement between your country and Thailand but you need to complete a Thai tax return to take advantage of that, so check the relevant agreement. I believe American SS is an example of income that is not taxable in Thailand due to the DTA but don't take my word for it. As to differentiating between savings and income you need to keep records, any income received prior to
*****
/2024 is exempt so that's a good starting point, savings accumulated prior to that date are easy but savings after that date must have come from somewhere (most likely income of some sort so the income counts)