Done some more reading and I have a more specific question now.
I've read the guide and if I understand this correctly, as long as the increase in price on my apartment took place before 2024, it will not be taxable in Thailand. There was a huge price jump in about 2020 when the appraisal process was changed. I would be able to document this with reports from the "cooperative apartment" complex I live in. I have not yet sold my apartment, but plan to do so later this year or early next year. This is the uncertain part for me, i.e. whether it needs to have been sold before 2024 or not. Any comments appreciated.
https://aseannow.com/topic/1324294-intr … e_vignette
48) The proceeds from the sale of a capital item such as overseas property, where funds are remitted to Thailand, is one popular source of expat funds, the sale of some investment products such as stocks, shares and bonds is another. Those proceeds typically comprise two parts, capital and profit (or gain). If the capital and/or gain was acquired before 1 January 2024, it is free of Thai tax. If they were acquired after that date, they are potentially subject to Thai tax at PIT rates.