Oh yeh you'd have to be a real sucker to take a significant pay-rise from being an F/O here to a skipper in Singapore, paying much less tax
Unfortunately, the labor government recently changed the tax laws. This means (for most people who go on temporary/short term) if you pay less tax overseas, you will then have the pay additional tax to Australia. Therefore you will be paying the same tax as in Australia.
See this document
http://http://law.ato.gov.au/atolaw/.../NAT/ATO/00001