UnionPay has a wide business scope and can be used in many places in Southeast Asia, provided that both POS machines and ATM machines have the UnionPay logo.

Airports, large hotels, these places should be basically ok.

However, it is recommended to exchange Thai baht in China before going out. It is unsafe to withdraw cash by credit card in Southeast Asia, and it is easy to be stolen. I will want to cry when I come back.