There's heaps to do in Changi. Many Singaporeans go there for fun on weekends, especially now that the train station has opened.
Also, there's this game show in the transit lounge which transit passengers can take part in, and is a bit like Who wants to be a millionaire, except that you just win $1000 or something like that.
There's also a small cinema where you can catch HBO movies. Which means the movies will be at best 1-2 years old.
If you have a lap top, you can log on to the internet at the many free internet connection booths in the transit area.
Changi doesn't have the kind of modern architecture we see in HKG and KUL, but it's bright, cheerful and comfortable and is in no way ageing.
6-8pm are the busiest times of the airport. Most of the first wave of European flights come in between 4 to 6.30pm (the second wave comes in at 6.30am) and most of the Aussie flights leave at 8pm. Which means you'll see heaps and heaps of Qantas planes. (That's at Terminal One though)
Ryan, how long will your transit time be on your way back from BKK? If it's at least 4 hours, you can take the free Singapore tour and have a first hand feel on how our clean and perfectly-organised, prim and proper city combats the evils of jaywalking, spitting and gum-chewing, which could prove detrimental to our economic well-being!