From everything I’ve read, It is monies earned in or remitted to Thailand being taxed, whether it is from savings or income. Monies earned or saved outside of Thailand and never brought into Thailand are not taxed.
Savings are taxed only in the amounts that are remitted to Thailand by whatever means (transfers or ATM withdrawals) and only those savings deposited in whatever type of savings account after 1 January 2024.
“Retirement” income is taxed, again, only in amounts remitted to/brought into Thailand, depending on any tax treaty with your home country that may make it exempt, and if taxable, double-taxation prevention considerations apply (as they do with other types of monies brought into Thailand.)
It was great. I had veneers done in Bangkok. Aside from having no clue what they were saying apart from “Hollywood Smile” and the price, it went off with lout a hitch. All done in less than 10 days. I’d suppose time depends on what you need to have done.