you can go to main express bus station which PUDURAYA BUS TERMINAL in Kuala Lumpur. Express buses are faster way to go to singapore 5hr i think. Beware of the pick-pocketer there. Ask the Chinese there, they will show u which ticket counter to go. Alternatively, get express bus (super coach) to Johor Bharu then in Larkin Terminal get Singapore-Johore Express to singapore. Train is slower than bus in Malaysia
To check the website of time table is
Train Timetable in Malaysia
transport info
visit malaysia website
wish u have a nice trip
http://www.seat61.com/Malaysia.htm