3. Notwithstanding the provisions of paragraphs (1) and (2), remuneration derived in respect of an employment exercised aboard a ship or aircraft operated by an enterprise (for example China Southern) of a Contracting State ( China) in international traffic (I would interpret this as anywhere outside of China), shall be taxable only in the Contracting State (China) of which the enterprise (China Southern) is a resident (China)
I've entered my comments in brackets. IMHO I wouldn't bother with a tax professional . I'd just get a ruling from the ATO for peace of mind. As I mentioned many CSA pilots have already done this.
If this paragraph doesn't apply to you and you are an Australian tax resident, I would imagine some top up tax would be applicable. Unfortunately many Chinese airlines are in low tax areas and pay bugger all tax which doesn't help. It may be worth asking an agent ( like GABS or Longreach) for an example of a Chinese payroll tax certificate ( which will be in Chinese unfortunately ).