Singapore is one of the safest major cities in the world by virtually any measure. Most people, including single female travellers, will not face any problems walking along the streets alone at night. Do be aware of pickpockets in crowded areas and don't forget your common sense entirely.
In an international quality of life survey, Singapore ranked second after Luxembourg, and alongside Helsinki, Zurich, Geneva and Bern in the personal safety category. Its crime rate is also one of the lowest in the world. While 2005 saw an increase in the overall crime rate, it was mostly as a result of minor crime like theft from homes, or of mobile phones and bags. It’s silly to leave valuables unattended in public places, especially laptops. Travelling by public transport and taxis, however late at night, even if you are female and alone, is safe.
While not commonplace, women in bars and nightclubs have had their drinks spiked, so don’t leave them unattended. A reliable way to start a fight is to stare at someone; men interpret it as an affront and the customary response is belligerence.
On the road, watch out for motorcyclists as they often don’t follow road lanes and squeeze in between cars to overtake or get to the front of the traffic. Singaporeans are so accustomed to following explicit rules that when lane markings are absent (due to road works), they become befuddled and lane discipline breaks down.
Singapore treats drug offences extremely severely. The death penalty is mandatory for those convicted of trafficking, manufacturing, importing or exporting more than 15 g of heroin, 30 g of morphine, 30 g of cocaine, 500 g of cannabis, 200 g of cannabis resin and 1.2 kg of opium, and possession of these quantities is all that is needed for you to be convicted. For unauthorised consumption, there is a maximum of 10 years' jail or fine of S$20,000, or both. You can be charged for unauthorised consumption as long as traces of illicit drugs are found in your system, even if you can prove that they were consumed outside the country, and you can be charged for trafficking as long as drugs are found in bags that are in your possession or in your room, even if they aren't yours and regardless of whether you're aware of them.
For some crimes, most notably illegal entry and overstaying your visa for over 90 days, Singapore imposes caning as a punishment. Other offences which have caning as a punishment include vandalism, robbery, molestation and rape. Do note that having sex with a girl under the age of 16 is considered to be rape under Singapore law, regardless of whether the girl consents to it and would land you a few strokes of the cane. This is no slap on the wrist: strokes from the thick rattan cane are excruciatingly painful, take weeks to heal and scar for life. Corruption is also punishable by caning so under no circumstances should you try to offer a bribe or gratuity to a police officer. Crimes such as murder, kidnapping, unauthorised possession of firearms and drug trafficking are punished with death.