I have a second cellphone I use as a wifi hotspot for my us phone. My tello and mint do wifi calling back to the USA for 0 extra. If I want to call local use line or for real call I need to add talk time to plan, as I only have $10 a month data on the AIS sim
You can come and go by air as you please as long as you don't appear to be living long term in thailand. So you can do visa exception, leave when you need to, stay 10 to 30 days in another country and Thailand will welcome you back. (Try to spend less than six months in the year in Thailand.
You pay another 10,000 baht to come back for another 180 in the same year. You must prove you have 500,000 baht in a bank somewhere in the world and have a freelance job with proof of work somehow
Put a few other countries stamps in your passport, cheap like Malaysia, or Indonesia to make you look like a tourist. Once in a while I forget that it's in my pocket and I accidentally put it in the washing machine, which has caused me to discover that many countries stamps aren't waterproof