I'd like to do a daytrip from Singapore to Kuala Lumpur. From what I've seen, the length of time it takes to get there on a coach or train is too long to make this work, so I guess I'll have to fly.

Which airlines are the best for this? I checked Malaysian Airlines and they have about five round-trips a day, which is great. But you can't book on the internet more than 48-hours in advance. Any other airlines or suggestions for making this a reality?