For my experience in the public, (I believe it's very common for most bros here)
1) Staircase @ Jurong West
Was there with my ex, did bbbj and CIM.
2) Staircase @ Bukit Batok
Was there with an online gal, did doggy and cum on her face.
3) Jurong West Multi Carpark
With ex, she sat on my leg as she wearing skirt, so did riding and finish with CIM.
4) Yew Tee Shared Rubbish Bin (Those new housing has rubbish bin outside their apartment)
Was sending my ex home, felt horny and did it there.
5) East Coast Park (Building a tent)
Was there with a girl i met in the club, contacted her a few days and decided to have an overnight at ECP, did it there for that night.
As i am living in the west last time, had much places to go, now living in northern side, hope to get to know more place to go 