This seems about right, on the proviso that the checkin staff in KUL can tag your bags all the way through, past SIN. I wouldn't see this as a problem, but you may have a slight hitch as JL and NW aren't part of the same alliance, I don't think this is a real issue though.
You are unlikely to get your boarding pass in KUL, but they will most likely tag your bags all the way through, with flight number (if others have had difft on varied non aligned carriers, pls advise on here). In SIN they have very large transfer desks for airlines (complete with pull a tag and wait in the queue system) in both terminals for you to be issued with your boarding pass. Don't expect to receive this boarding pass on NW stock.
I think staying in the airport hotel is the way to go (as long as you can find a room - book early being the important thing), also good idea staying at the airport, particularly with such an early flight, as well as having visited SIN earlier on in your trip. I have heard SIN Silver Kris lounge can get seperate allocations of rooms in the transit lounge, that's if you can get it and ask them if you do have difficulties getting a room.
There are no earlier flights on SQ/MH to get you in for your 6am NW flight. JL is fine. The service is exactly the same as SQ/MH, don't expect a full international service on this 30 min flight.
Hope you have a good trip, and looking forward to hearing a trip report when you get back!
Also, try and limit your time hanging around the KUL KLIA terminal, it's dead boring. I would strongly suggest catching the KLIA Ekspress if travelling in a party of 1 or 2 from KL Sentral (which joins to the Putra and KTMB lines). Allow 28 mins to get to KLIA, with 15 min regular departures from KLIA and KL Sentral, on the dot. You will need to allow time to pay at KL Sentral, at KLIA you can just jump on a train and pay when you arrive at KL Sentral. They accept credit card through machines at KLIA, and over the counter by payment of cash or credit card at KL Sentral. KL Sentral has a regulated taxi fee which can get you to all areas through KL / Petaling Jaya (be warned, arriving after 12am to catch a taxi incurs a further 5 or 10 RM fee, additionally the trains on Putra close from around 11:30pm. Luggage is a supplementary RM1-2/piece).
[This message has been edited by kawoh (edited 03-12-2003).]