Going there in November for a month. I have a Thai bought phone with Thai sims. Would I remove one of them there and replace with a US sim for the month? Also, I use the Line app for calls here. Has anyone gone back there and used it?

No replies after a few weeks?

 

OK, generally it should be fine to use a phone acquired here in the U.S.  But you need to check your device's frequency bands for compatibility with the U.S., and even the frequencies used by the various U.S. service providers.

 

Go here and input your phone make and model in the search bar.

 

https://www.kimovil.com/en/

 

For example, I put in Realme 9i, a fairly new model.

 

https://www.kimovil.com/en/where-to-buy-realme-9i

 

And it says, in the case of this phone, there are six versions. You check and select the version which matches the phone for which one wants to get info about, whether your phone or one you might want to buy.

 

Then scroll way down till you see Kimovil Frequency Checker.  If you've opened the page here, Thailand is probably the default country showing in the drop down menu. Change it to United States and you will see which bands the phone has which are compatible with frequencies used in the U.S. Furthermore, you can even check for compatibility with the various main service providers a little further down the page.

 

2G, 3G, 4G, 5G, they're all listed there. (Although I've heard some providers are now phasing out 3G? I don't know for sure about that.)

 

This will let you know if a phone from here is going to get the job done there. And if the phone is compatible with the service provider, swapping SIM cards will do the trick. 

 

LINE, no problem using it for making calls on LINE while in the U.S.