If you didn't have the airline authorize your return via other methods (often known as Rule 80, which means they endorse your ticket to another airline,) you should not expect they would reimburse you for a walk-up one way fare home.

OTOH, your credit card company may, as otherwise have clearly pointed out, be of some recourse (but don't expect more than half of your round trip fare credited to you if the chargeback is completed.)

I do recommend checking airline reliability, etc. You are talking about an airline operated by one of the most corrupt authoritarian governments around, one which still includes Khmer Rouge leadership (which killed ~1.7 million people when it was totally in charge.) Not too much compassion there, I am afraid..