It's quite easy for a foreigner to get credit cards in Thailand, 3 scenarios:
You don't have a work permit and you don't have money in the bank : no credit card
You don't have a work permit but you get some money in the bank : you can apply for a "secured credit card"
You have a work permit : you can apply for a credit card
Years ago, I was in the scenario # 2 and I got a secured credit card.
When I decided to be based in Thailand (with a TH work permit), I applied for a credit card and got it!
PS: When I was based, as a foreigner, in Czech Republic, Ireland, Kenya, UK, the rules were quite similar: you have a job then you can apply for and get a credit card