Others have already replied this is not exactly the case and it's trafficking weed and other drugs that gets you hanged.

That being said, I'm not so chill about weed. Weed people, like smokers before them, don't consider weed to be a big problem for the people around them and ignore anything you might have against it. That means you'll be laughed at when you ask neighbors to stop smoking two floors below you, to stop growing the plants in their tub, etc. It also means you'll have to go through a lot of places that smell like shit because people smoke weed there often.

Only for quantities consistent with trafficking, meaning a minimum of 500 grams. You won't be hanged for a joint.

You may, however, be sent to the Drug Rehabilitation Centre, which is co-located with and effectively a part of Changi Prison, and about as pleasant. Most first-time offenders get away with a probation scheme called the Enhanced Direct Supervision Order though.

You can also to to jail for selling chewing gum. And you are legally required to flush a public toilet after using it.

They also seem to be one of the few countries that won the war on drugs, no?