(https://en.wikipedia.org/wiki/Misuse_of_Drugs_Act_(Singapore...)
> The law creates a presumption of trafficking for certain threshold amounts, e.g. 30 grams of cannabis. It also creates a presumption that a person possesses drugs if he possesses the keys to a premises containing the drugs, and that "Any person found in or escaping from any place or premises which is proved or presumed to be used for the purpose of smoking or administering a controlled drug shall, until the contrary is proved, be presumed to have been smoking or administering a controlled drug in that place or premises."