First point everything is back to normal since covid.
More importantly is that clearly you have no idea regarding flying visa exempt.
The airline from Oz most likely will require you to have onward flight within 30 days.
Which airline is your flight?
Here is recent thread ...
https://aseannow.com/topic/1294354-onward-ticket/.
https://aseannow.com/topic/1293995-proof-of-onward-travel/