See -> Change your Apple ID country or region
Change your Apple ID country or region - Apple Support (KW)
You need to have a debit / credit card issued by a bank in Thailand.
You need to have a billing address in Thailand
Then -> Sign in to your Apple ID account page and edit / update your Apple ID details.
https://appleid.apple.com
- On the Sidebar click Payment methods -> then tap Payments Methods and tap Manage payment method.
- Edit your billing address .
If you update your payment method or add funds to your Apple ID balance, It would take about 1 to 3 business days in order to process.
If you're still unable to update your payment method, Contact Apple Support.
Click here for more support and assistance.