Didn't IATA create Timatic in the first place to resolve these issues? CZ is an IATA member. Seems to me that if an IATA member airline is saying Timatic is wrong, they better be able to back it up and get Timatic updated so the issue does not recur.

I'm inclined to believe in this situation, Timatic is probably right. US Gov web sites are irrelevant. Thai immigration law experts generally aren't English speaking web designers, and Thai English speaking web designers generally aren't Thai immigration law experts, so Thai government English web sites are probably best taken with a grain of salt. I suspect CZ screwed up, OP is owned compensation based on CZ unilaterally making up a rule inconsistent with Timatic.