Three airlines who fly to australia do so via Bangkok - British Airways, Quantas and Thai airways (there are probably more), so a "stop over" in asia on the way to or from Oz won't cost extra... just a thought

Often you can get two stopovers, and most flights to NZ are via Sydney, so if you have the time you could tour asia, Oz and NZ all on one ticket, for the same price as a simple return ticket. You can even combine with an extra leg for a smallish amount as in this example:

leave in the autumn, start with a loop from/to Bangkok via Laos, Vietnam and Cambodia (nov-dec), fly to Auckland, ride down and round to Christchurch (jan-feb), fly to Cairns (extra leg, SYD-CNS) ride down the coast to Sydney (mar-apr),... then home in time for spring... tada! no cold winter!!!