As a general rule, Air Asia have a check-in fee if you're not using the online/mobile check in option on their website. However, this seems not to be applicable to all flights; does anybody know why it is not applicable on Thai Air Asia flights for instance?

So am I right in assuming that depending the operating branch of the Air Asia brand you're flying with, you either have to pay it or not then? And how does this work at places like BKK, where different brands operate on the same route, one with and one without the check-in fee? Why not streamline this process? Quite confusing, I must say!