spicysalad

You are right. I just called 1678 again and got an agent this time. She changed my 'package' from tourist to regular prepaid SIM and said I can continue using it as normal now with no monthly fee and can continue extending the validity by topping up.

I got a very similar message from DTAC but the date is 14 Jan 26 for me. After receiving the message I did a series of 10 baht topups to extend my validity out to the maximum 1 year. I'm assuming that I'm good for another year from now but any top ups made after 14 Jan 26 will no longer extend the validity any longer? What happens if I want to extend it further in the future? I guess I can do that by re-identifying myself at a True dtac shop or calling 1678? Will they make me buy a package to extend the validity? Or what exactly do I need to do to extend the validity other than identifying myself? I've had this number for almost 4 years and I use it as a permanent number to receive SMS codes for banking, etc and incoming calls. I don't have any package and just do 10 baht top ups to keep extending the validity. I use another SIM for data and outdoing calls which gets changed every year (Annual SIM card packages from Lazada). I called 1678 to ask for clarification because this message is confusing. I was put on hold for 15 minutes and then told there are no agents available. I was still charged 3 baht for the call even though I wasn't connected with an agent.

What you were told is not exactly correct. You may still be able to get all of the withheld tax back even if it exceeds 20k. When you file your tax return you have the option to have interest taxed as regular income instead of the 15% withholding. If your total taxable income in Thailand is under 150,000 then there is no tax owed. So if bank interest is your only source of income taxable in Thailand then you can get all of the withholding back if the total annual interest received is less than 150,000. Above 150k is taxed as regular income. If your Thai taxable income is very high then it could be better to just pay the 15% withholding instead of making the declaration to treat it is regular income. The 20k limit is the threshold that the banks are allowed to exempt you from withholding. After 20k they need to apply withholding, which you may be able to get back in whole or in part depending on your total income for the year. To get this 20k exemption you need to provide a tax id.

I believe the only way is if you are female and marry a male Thai citizen.