I see nothing but what women should wear in singapore but nothing about men.
I would like to know what do men wear in singapore day and or night.
On the streets, generally, whatever men wear in the US during the summer months would be suitable in Singapore. Flip-flops are acceptable too.
Clubs and upscale restaurants may require formal wear or business casual. Flip-flops, sleeveless shirts, and shorts are not suitable for such places.
At religious places, shorts and sleeveless shirts are not allowed. For business etiquette and what to wear when on a business trip in Singapore, check out this short article, Business etiquette in Singapore by Marina Bay Sands.
You want to have your own suits custom made there. That is the best. They are the finest tailors. You can tell. My son had his made there.
As Claus points out, it's best to dress comfortably for tropical heat, i.e. lightweight and loose-fitting clothes. Local standards of dress are a bit more formal than in North America and parts of Europe...adults who wear shorts in public will be seen as underdressed, and wearing T-shirts with logos and slogans plastered all over them is also considered a bit too casual. Slacks or blue jeans and a short-sleeved button down or plain T shirt should be fine during the day, and maybe dress a bit smarter at night.
You should wear something light, as Singapore is located right on equator. But unless you walk around in some very skimpy clothes, or you walk around bare chested, then you have no worries. Singapore is a multi national and multi cultural city, with people from all over the world living there. So it's not like there is a dress code. Same goes for women for that matter. You will see anything from people who are covered from top to toe, to people in tank tops and shorts. And we are talking local people from Singapore here. Very very few cities in this world are more international than Singapore. so they are used to a bit of everything.