So I must be very
lucky
, there is a period when I was dual citizen.
The Aussie side did not ask me if I have renounced my Singapore citizenship. It just remove my PR visa. So, I do not need to report I renounce Singapore citizenship.
I travelled in and out of Singapore using both my Singapore and Australian passports without any issue.
On my Singapore passport, there is no OZ entry or exit stamps but Singapore immigration do not care.
When I fly to Singapore, I purchased my air-ticket using Singapore passport because I used a different name in Australia.
I showed OZ immigration my Oz passport. Only once did they found out that my air-ticket name is different from my Oz passport. No dramas, I just show my Singapore passport and Deed Poll and I was through.
Reach Singapore, I just use Singapore passport to enter.
But when flying back. I needed to produce my Singapore Passport at the Changi Airport airline ticketing counter because my air-tickets were issued in my Singapore name.
But when I enter Singapore immigration counter, I showed my Singapore passport. Remember, my air-ticket in Singapore name, so no need to show OZ passport.
When I land in OZ, I used my OZ passport. Home Sweet Home.
Compared to my time, I think Singapore is more relaxed about dual citizenship after LKY's speech and all the FTs coming into the island. Also, many elites and their kids are holding dual citizenship these days.
The point I want to make is - if you do not cause trouble in Singapore, the Singapore authorities will give you chance to select and renounce one of the citizenship.
But Singapore authorities are crazy sometimes, and if they may be a chance that they happy happy and arrest a dual citizen. (In Australia, they are not allowed to do that.)