Just today there has been news of someone wearing belts with buckles looking like a Knuckle duster being arrested and charged in court, although the charges were eventually dropped, I think there is a need to inform people in Singapore on what scheduled weapons are.


As extracted from the Singapore Statutes.

SCHEDULED WEAPONS

1. Any knife, sometimes known as a flick knife, which has a blade which opens automatically by hand pressure applied to a button, spring or other device in or attached to the handle of the knife.
2. Any knife, sometimes known as a gravity knife, which has a blade which is released from the handle or sheath thereof by the force of gravity or the application of centrifugal force and which, when released, is locked in place by means of a button, spring, lever or other device.
3. Any whip manufactured from bicycle or motor cycle chains or from any similar kind of chainwork.
4. All kinds of knuckledusters.
5. Any blade or other instrument attached to or forming part of a bicycle pump, metal-pipe or stick, and concealed therein, which is capable of being used for cutting or stabbing.
6. Any sword, machete or parang, axe, sickle, bearing scraper, spear, bayonet, iron rod, and the nancha-ku (segments of wood or metal joined by a chain, leather strap or cord).


So I think that's why Swiss Army Knives and Multi tools are exempted since they don't have a mechanism for flipping the blade out.

Below are some links to new stories and the Singapore Statutes.

Links
Harsher penalties and fines for scheduled weapons in S'pore (The Electric New Paper)
Singapore Statutes (Look under Corrosive and Explosive Substances and Offensive Weapons Act)