Before you go to any country, it is vital to check up on what you are not allowed to bring in with you. Chewing gum is allowed for therapeutic use only, and this is upheld by Customs & Excise officials to the letter. They do now allow room for negotiation, and, unless you are seriously addicted to the stuff, it's no big deal anyway, and certainly not worth the risk. Tobacco products are not duty-free.

Items that are forbidden from being brought into Singapore :

• Alcohol and tobacco products (including cigarettes) intended for export. These may carry a sticker ‘Singapore Duty not paid', or in the case of cigarettes if they have the prefix ‘E'. Also imitation These are not allowed to be consumed in Singapore .
• Chewing tobacco, or any imitation tobacco products
• Fireworks
• Lighters that look like a firearm
• Board game money
• Reproductions of publications, cassettes, DVDs, CDs or other materials that are copyright protected
• Wild animals, or species threatened with extinction (and their by-products
• Pornography
• Subversive or seditious materials
• Chewing-gum
• Controlled drugs

Please be aware that Singapore has very strict anti-drug laws, with drug trafficking carrying the death penalty. In fact, if you are carrying the keys to premises where drugs are used/kept, are caught in the company of someone using drugs, or are caught fleeing the scene where drugs have been used or kept, it will be presumed that you are guilty of using and possessing, unless subsequently proven otherwise. Punishment for drug offences include long prison sentences, caning, and capital punishment.

There is no limit on the amount of local currency you may be bring in to Singapore .

It would be advisable to check the Singapore Customs' website before packing:
http://www.customs.gov.sg/topNav/hom/