Cmd,
The Ambassador Transit Hotel is a pretty good place (small rooms). 6 hours= 48 USD.
The terminal plus the terminals (airside have lots going on) up until 24:00. There are restaurants and the bookstore is open 24hours. There is a 24 Gloria Jeans. The ambassador hotel also has a free fitness center. Terminal 2 has alot more activity (including a free movie theater). ID you take the KUL-SIN shuttle asn end up on SG youll land there. It is funner to hang out there than Termainal 1. Remember though the inter-terminal train stops at 01:30 so you'll have a long terminal to terminal walk if you miss it. Go to the Subway and get a sandwich doubled wrapped to go so you can have a real lunch once you get to NRT as the Worldclub has zippo food.
Puck
If this is you honeymoon make sure you get a room at the Ritz at least above the 11th floor. And definitely kick in the extra $50-75 USD for a corner "Suite" room. It is the best deal in town. I can give you the name of a consolidator if the Ritz asks for more than that--a much larger room with corner view. The best is obviously the Singapore city skyline view--the back bay ones are that special for a honeymoon. The bathtub view will make this a special stay

. So romantic it could make you fall in love with Joan Rivers. The best rooms are the corner ones on the SOUTWEST side. The spa isn't so great but the pool is excellent. Sometimes the staff says rooms above the 11th floor are not available...Ask politely to speak to the Duty Manager. They were trained by Ritz in ATL not Marriott so they are very accomadating.
Happy Honeymoon!