Please apply Australia Visa 1-2 months before departure.

A) If Visa is rejected, it takes 2-3 weeks for the Immigration to process.
B) If rejected again, takes another 2-3 weeks to appeal with New supported documents

Case 1
Old Passport : Visa approved
New Passport : Visa rejected

Case 2
Old Passport : Tagged to APEC card (With Australia Visa)
New Passport : Didnt renew APEC card. Visa rejected.

Case 3
New Passport : Infant - below 12 months (Visa rejected)

Case 4
Old passport : Working previous in Australia. Already quit the job and left Australia.
New Passport : Visa rejected due to some Immigration matters not settle during employment period

Case 5
Current Passport : Visa approved
Enter Australia and stay almost 3months (about 87-89days) in Australia.
Left Australia and quickly book a return ticket back to Australia two days later.
Eg
Australia-SIN on Friday
SIN-Australia on Sunday

At the Airport, Check-in staff (Airlines) didnt issue boarding pass.
Australia Visa denied and suspended immediately. Cannot board the plane.
I asked pax whether is he working illegally in Australia, he didnt reply.

Sorry, we wont know the reason for the Rejected Visa.
Maybe applicant will know. We dont ask.

Or apply Australia Visa before you purchase the air-ticket
Dont take things for granted and wait till last minute.
Thanks
Kang