Presumption of possession and knowledge of controlled drugs 18.—(1) Any person who is proved to have had in his or her possession or custody or under his or her control — (a) anything containing a controlled drug; (b) the keys of anything containing a controlled drug; (c) the keys of any place or premises or any part thereof in which a controlled drug is found; or (d) a document of title relating to a controlled drug or any other document intended for the delivery of a controlled drug, is presumed, until the contrary is proved, to have had that drug in his or her possession.

A friend leaves a key to a locker in your apartment. It has half kilo of cannabis. The cops find the key in your apartment? Toasted.

> (1) Any person who is proved to have had in his or her possession or custody or under his or her control

So no, as much as you want to think of Hollywood-esque scenarios where a friend or some random plants a drug on you, which gets you the death penalty for being completely innocent, you actually get a lawyer and a trial in court where you can prove your innocence. Singapore does not do kangaroo courts. The prosecution needs to prove beyond all reasonable doubt that you conspired with said friend to hide the key in your locker. And needless to say they also have to prove you had the knowledge that said key controlled access to narcotics.

And chances are, this has never happened in reality because drug traffickers into South-East Asia are an extremely close-knit group who in general don't go around handing 'drug locker keys' to their friends and random people on the street. The law exists to prosecute conspirators, not randoms.