When I did the exact same journey a couple of years ago there was not a stopover option to leave the plane at BKK and then reboard at a later date to continue to HKG (HKG passengers stay on the plane). You could do it, but it would have to be a separate ticket from BKK-HKG, which I presume would present difficulties as the turnaround on the ground is <1 hour.
Very nice airline though - outstanding food, albeit on angled flat seats. 560TPs