Thanks for the reply.
Apparently Jetstar is cheaper from Sydney to Auckland so I think I'll book their tickets.

My timeframe is as follows: I'd like to leave for Thailand in mid August for 1 month, China for 1 month, Australia for 3 months and New Zealand another 3 months. This is the approximate timetable.

The idea of visiting Macau and getting there on a ferry is pretty exciting. However, Viva Macau seems kind of a dodgy airline, with only two planes.
As for the price, I guess it will be about the same, with a little less hustle (not having to get back to Bangkok).
I actually kind of like to idea of arriving in Perth, because that would allow me to travel in Australia - coast to coast and then continue from Sydney.
But anyway this is worthy suggestion, I will most certainly consider it. Thanks!