The quarantine is no longer in effect effective May 1, you just need to have proof that you had Covid vaccinations, or if you don’t then you have to go to a hotel or have a negative test before you come in 72 hours
But I do carry two phones when I’m in Thailand, I could get a Sims card for one of them. But we use the application line to communicate with each other in Thailand so I really don’t need a local Sims card
I’m not there now I’m in the United States I’ve only been there for one month at a time the last eight years, I used to be with AT&T and they screwed me in international travel T-Mobile Was 4G service when I first started using it in Thailand but a few years ago they switched to 2G although I do get it throughout my whole stay.