I bought two tickets online for myself and a friend HKT-BKK, but we were travelling on different flights. I checked in first and his flight was 6 hours later. So he stayed at the hotel to relax at the pool and when I was at the airport, I showed them the cc and signed a little receipt. They put a note into his reservation showing that I had already provided the CC used for booking. It worked. They let him check-in without any problems. But, from my experience, they are really strict about this. I think it is ridiculous, but my opinion doesn't matter.