You don't use the US zip code system in Thailand? Unbelievable!
At any rate, your card was declined. That means they said you have no credit available. You have to have a valid card with credit available. That shouldn't be hard to understand.
Yes, it's not really free if you have to have a method of payment...
Here are 20 threads where people discuss the meaning of the word free:
http://www.chess.com/forum/search?keyword=free+trial
I want to try the 10-day premium membership but it says
Your card has been declined by your credit card companyy. Please try a different card or contact your credit card issuer for more info. This can sometimes happen if you misspelled your street address or did not provide a correct ZIP code. Contact Chess.com Support for help or additional payment options.