The MH bus transportation runs from the Copthorne Orchid Hotel in Singapore. The fare is SGD$12 and it brings you direct to Senai airport. The buses are timed to meet all flights leaving from Senai airport. In good traffic conditions, I reckon it will take about 45 minutes by cab to get from the Singapore airport to the Copthorne Orchid Hotel.

Now, I did this about 4 years ago, and I'm not sure if the procedures are still the same. But at that time, it was a one-stop process, where you show up at MH's office in the hotel, where they will do the check in for you right then and there. ie. obtain boarding pass, take your bags, tag it, and send them on their (and your) merry way. You get onto the coach, pass customs and immigration to enter Malaysia and voila, you're at Senai and waiting to board your flight.

For further details,
http://www.malaysia-airlines.com/sin...oach_serv.html

There is also a link on that page showing the schedules. (ie. which bus to take for what flight). Your best bet would be to ring MH Singapore for reservations and information.

I would also recommend perhaps overnighting at the Copthorne Orchird Hotel itself so you wouldn't need to worry about getting yourself from the airport to the hotel ontime to catch the bus. It's a decent 3 star hotel off the tourist belt, so it shouldn't cost much.

Have fun!