Thailand is a straightforward eSIM destination if the phone is unlocked and the plan is installed before you land.
City week or island hopping
A Bangkok week with hotel Wi-Fi is often fine on 5 GB. Island days with maps, ride apps, and photo uploads are safer on 10 GB.
After you land
Turn on the Thailand line, set it as mobile data, and enable roaming for that line. Keep your home number active for texts.