NWR,
Since this is not a Mileage-Run-specific question, but rather a question about SIN airport and layovers, there would be a lot of info in the Destinations forums. Did you know about the Singapore forum?
http://www.flyertalk.com/forum/singapore-510/
A good proportion of threads are questions and answers relating to SIN airport itself - what to do, if it is worth doing the free city tour, lounge and entertainment or shopping options etc.
e.g. this recent one:
http://www.flyertalk.com/forum/singa...ction-sin.html
There are lots of free internet-access terminals in the main concourses, thousands of shops and places to eat or drink, various lounges, a free movie theatre and outdoor areas, plus an option for a free tour of a few tourist attractions, sponsored PR from the Singapore Govt.
If you have lounge access through staralliance, you could check on threads about the lounge options. I have sometimes found a lounge or part of it is closed for renovations, so it is good to check on the current state of the lounges or anything else of interest.
Here is the forum. Have a good Mileage Run!
BiziBB, Moderator Mileage Run forums