When i went to Singapore people told me how bad it is and you're not even allowed to throw trash on the street and might get to jail for spitting your chewing gum on the street. Sooooo, you're saying I'm perfectly fine in that nice city then?
I mean your examples are trashy things to do in the first place. If you're traveling to other countries and your main fear is "am I allowed to litter here" then it's best you stay home.
Singapore has a lot of intense laws, and they enforce everything fairly strictly. That being said, almost every country has littering laws, just because they're not enforced doesn't mean you should litter.
Possession or consumption [of cannabis] can result in a maximum of 10 years in prison, with a possible fine of $20,000, as well as caning, under the Misuse of Drugs Act. Trafficking, import or export of more than 500 grams may result in the death penalty.
As we say her in the USA, let the punishment fit the crime. There's a Star Trek episode where Wesley gets sentenced to death for walking on the grass or something like that... Singapore is basically that.