If there is a problem, they'll catch it when they scan your boarding pass right before you enter security, and then send you over to Cathay to fix it. I've been sent back before because my online boarding pass didn't register when they scanned it. No big deal.
Doesn't affect your departure tax situation, since you're leaving the same day you arrive.
Thanks for that. Very helpful. So I should just go via the CX check in counters anyway to have them register my boarding pass so as to get thru the initial security check.
Good to know about departure tax. I did the same at BKK recently, but the layover spanned one night, and when re-checking in, had to pay 700 baht airport tax.