Hawker centers are very popular places at all hours of the day and night....good food and good fun even if you are alone. Oh yes, I agree on the restaurant/bar selections also. Clearly you may wish to stop at a Hawker Center first then make your way to the "entertainment cluster" areas. I happen to prefer Boat Quay and always visit the Northern Indian "Our Village" in that complex when I am in Singapore. The address by the way, if I recall is 46 Boat Key, but I am not certain they are open at the time you will likely be there. Many boat Quay restaurants/bars will be open and you can enjoy a beverage on the shore of the river and the lights which illuminate the quite attractive Hotel Fullerton,some nearby high rise office buildings, and several important government complexes across the river from Boat Quay.

As you likely know, SIN is an inexpensive place to grab a taxi and since the areas you will likely visit are clustered close to each other, I suspect that your local bill will be less than $S20 for the intracity portion and the RT to the target area from-to the airport should be less than $S50 total. By the way, you may wish to have the taxi trip to/ from the airpot include a brief drive-by one of the more famous but at that time of the night closed shopping area of Singapore, Orchard Road. (Just ask the taxi person what the incrmental cost would be---a few bucks at most.)

Have fun!

747LWW