Tax depends on where you get paid. Totally-tax-free FIFO is a thing of the past as most Governments are onto it.
If you can, draw the bulk of your salary in Aussie dollars and pay your tax here like a good citizen. If you can, negotiate a minimal living allowance in Kina. Of course this scenario may no longer be possible as APNG is now a Public Company listed on the PNG Stock Exchange and no doubt they have to play by local rules.
PNG has a 'no double tax agreement' (or whatever it's called) with Australia but it won't be much consolation if you end up fully paid and taxed in Kina.
At least with Aussie tax, you get something for your money and also can get some write-offs for investments etc.
As always, a good accountant's advice is what's needed before embarking on overseas adventures.
APNG itself is pretty straight as Companies go. They pay only what they have to, to meet the market, but at least they pay it on time.
For the experience, a great first job.