Singapore is fantastic for variety and safety. There's a large number of perfectly legal brothels, and perhaps an even larger number of streetwalkers, bars (the "4 floors of whores") and incalls that are illegal but more or less tolerated. It's definitely not as cheap as other destinations, but you can do stuff like pick up a Chinese girl at a brothel one day and a Thai girl at an incall the next and pick up a Viet girl at Orchard Towers the 3rd.
It's also a very safe country, the food is fantastic, and it's the center of everything, so if you want to take a side trip to Kuala Lumpur or whatever, flights are easy.