thar method works perfectly for me. I kept my tmobile account (SIM) from usa and added AIS esim for data and calls. I set the AIS as the primary and tmobile as backup.
Works perfectly. No extra charges. No issues with the esim settings at all.
It's possible you have an incorrect setting or an issue that is Verizon specific.
yes it does. Keep the US sim installed, add the esim, then choose the esim as the primary sim.
This is what I do and am able to receive texts and calls from USA and use the Thai esim for data on a daily basis. No need to buy a second phone, swap sim cards or any of that mess.
The prerequisite is that the phone must be unlocked and it needs to be a recent phone that allows either sim+esim or multiple esims.