Did you buy the Mint SIM in the U.S.? When? Did you activate it successfully there? It worked fine and then when you got to Thailand it didn't?
Yes I bought in the US it worked . It didn't work in Thailand because when I arrived at Bangkok airport I switched it out for a AIS sim card and put the mint sim card in my old I phone.
I bought a new I phone in America before I came to Thailand . Instead of trading it in the rep at the Apple store said keep it and put your American sim card in it when you get to Thailand except old phone didn't recognize the mint sim card.
Follow up- I went to AIS store in Lampang ,they put their sim card in my old i phone and put the mint sim card back in the new I phone.
IT WORKED ! I now can receive texts to my American phone number while in Thailand the mint service is 15$ per month.
Where did this "old" iPhone come from?