There is no fast track lane at Immigration for business/first at HKG, only e-channel for residents/frequent visitors. If flight is on time you will have plenty of time to pick up bags, head upstairs to departures and recheck them. Inbound and outbound immigration at HKG tends to be fairly swift even without e-channel. Don't dilly- dally coming off the plane though as a train ride to immigration is required. If all on time should still have a bit of time for a lounge. I would just see what gate the BKK flight is leaving from and pick the OW lounge nearest. QF/The Wing for lower gates. The Bridge for mid gates and if in 40/50's and The Pier for gates 60+.