Have a question guys I need to get a ticket from melbourne to either SIN,KUL,BKK ,Jakarta that I can change without any penalty or very little in economy or premium economy as I

Have a question guys I need to get a ticket from melbourne to either SIN,KUL,BKK ,Jakarta that I can change without any penalty or very little in economy or premium economy as I am then eligible for a cheap standby ticket on to europe with one of the gulf carriers - any ideas? obviously when i come back I need to be able to change the ticket if I dont get on the asia bound flight if its full ....Thanks again

Given its a stand by ticket to Europe, surely you will want a port with the largest capacity to the ME3 hub. I suspect that might be SIN. I find CX or SQ the most easy going about changes to return leg as long as inventory is available. 

Thanks again .

Flexible flights are generally not cheap, and often you still need to pay fare difference (which can be significant last minute)...

I would consider a couple of LCC fares a few days apart as a fall back (AirAsia, Scoot etc)

If you have frequent flyer points, you could buy 2 one ways on points, then cancel the return if you dont get on the flight you need.