All QF has to do is refund the BKK-SYD lfight legally or by QFF policy, so anything better than that is by goodwill or your good luck. The rules are different if travel had commenced (yours had not) or for paid tickets. My advice would be to ask nicely for award space to be opened, perhaps on a different date, and maybe accept via SIN. Going via NRT is not worth it unless you want to holiday in Japan too.
Frustrating that award seats have so few rights, but the airlines write the rules for their benefit. Sometimes having FF status helps with the goodwill, but you dont show any status.