Sorry you won't be able to do this (at least at Terminal 2) because the transit hotel is located in the secure departure area which is separated from the immigration arrivals area
You will need an onward boarding pass to enter the secure area.
Besides, with Terminal 2 at least, the rooms will most probably be full by 7am. There are at least a few flights that arrive at 6am-ish. I've only be able to snag a room twice (out of perhaps 15-20 flts) in the past when I've flown SIN-NRT or BKK-NRT.
[This message has been edited by tide (edited Jan 01, 2004).]