If you get award space on the direct flight, or via PEK, then go for them.
Going through BKK only has a plus if you are in business class or higher (I frequently do exactly this when in business, HKG-BKK-HND or HND-BKK-HKG, to enjoy the flights).
If flying economy class and have Star Alliance Gold, then it is mini-torture. If you can work in a long (20-24hr) layover, then it is a chance to get into the city, enjoy some Chang/Singha along the river, buy some I heart bangkok tee shirts, and then continue on to Hong Kong.