Singapore is a nation that holds a high standard for the integrity of its nation's assets and infrastructure. Due to this, there is a history of the nation meeting out several high-profile punishments against vandals of all forms. One such scenario was when a pair of tourists were handed the sentence of a caning due to their spray painting in the public trains of Singapore.
If you are yearning to enjoy some fine spray-painting artworks, simply head towards the neighbourhoods such as the Telok Ayer, so that you can fully immerse yourself in that experience as opposed to actively participating in it.