Consolidators in HKG : Hong Thai, Sunflower, Nan Hwa, Westminster, Swire Travel, Farrington American Express etc.
Have you tried booking on CX websites?
TG has the same route HKG-BKK-RGN-BKK-HKG for about HKD$2600ish and the class booked allow for 100% Royal Orchid Plus miles accrual..... FYI.