You could squeeze a few more miles out for little inconvinience (and perhaps even get a F class flight instead of J) if you did SIN-HKG instead of SIN-BKK. Both BKK and HKG have F flights going through to SYD, and there's always the pleasure of the Wing and the Pier to make the waiting a little more bearable if you've got the status or fly CX through to SYD (QF does fly in F from HKG-SYD too, though the lounge isn't so exciting in HKG for QF, but tier bonuses are always nice :D).