A Star Alliance Round the Planet fare is a virtually unbeatable way for you to travel the globe. For any individual heading to Australia, it can at times work out the same price tag to get a cheap rtw ticket (with one particular or two stops in Southeast Asia) as it does booking a return flight to Oz. Stop off in Bangkok or Kuala Lumpur en route, or wait till your time in Australia has ended and stop off for a beach vacation on your way home.
Second, the OWE rules do not carry any of the surcharges for certain routes/planes that you see with A. (Note the references from Don on Singapore’s or Air Canada’s surcharges – as much as $500 or $600 for premium-cabin flights on numerous lengthy-haul routes.) While some Oneworld airlines DO charge quite high fuel surcharges (notably British Airways) so do A carriers such as Singapore and Lufthansa.
The GlobEx would also suit the OP (greater in reality, given that Alaska Airlines is included as an eligible carrier) nonetheless originating in Oz for the OP’s route it really is more costly than a 4-continent OW Explorer (by AUD400) and AUD200 more than a YRWSTAR2 from Star Alliance.
Round the planet tickets can normally be altered for a comparatively nominal sum — so if you happen to be really enjoying oneself in Vietnam, you can choose to stay an additional week or two, pushing the onward flight to Singapore back rather than having to shell out for new flights.
Feel about internal travel: it CAN be less expensive to book internal flights at the exact same time as booking your RTW ticket – but, with the global boost of low-price airlines, you might locate it better (and much more flexible) to acquire them separately as you go.