I think the easiest thing to do would be to go into the Ultra Mobile app on your Samsung phone, convert the existing physical SIM to an eSIM, and install it through the app. Then remove the Ultra SIM from the Samsung phone and put in the Thai SIM. Once that’s done, you’re all set. Then you have both numbers working on the same phone. It shouldn’t take more than a few minutes. And if you change devices again in the future, no problem, you can just install the Ultra Mobile app on the new device, install a new eSIM, and you’re good to go. I believe they allow you to install the eSIM up to five times before they start charging a small fee.
