I did the same…Except I also have Google Voice for making calls over WiFi when I need to call the US. I just use my Tello number for Text to receive passcodes.
I ported my number from ATT to an eSIM a month before moving to Thailand. Been in BKK for a year. I’m on the $5/mo plan and use it for OTPs. I also have Google voice to make calls over WiFi.
so many variables on this that’s why I said “may have to pay tax”
One thing is certain if you’re in Thailand for 180 days you are a tax resident. Everything depends on the when and how the money was earned, your country’s DTA with Thailand etc.