u can drive Singapore registered vehicle if u are holding a tourist status (white card) for a 12 months. If u have any resident status in Singapore (eg, work pass, student pass, PR) you need to obtain a Singapore driving license to drive a Singapore registered vehicle. But u still can drive a Malaysian car into Singapore provided the following conditions are met.

a) he is the registered owner of the vehicle ;
b) he does not have a permanent residential address in Singapore and returns to his country of origin on a daily basis ;
c) the vehicle is kept or used outside Singapore for a total period of 6 hours or more everyday ;
d) he has a valid insurance certificate and road tax for the use of the vehicle on Singapore roads ; and
e) the vehicle has an Autopass Card to validate its entry/exit at Woodlands and Tuas checkpoints and for payment of Vehicle Entry Permit/Toll charges.

Please check LTA website for more info.

http://www.lta.gov.sg/motoring_matters/ind...oring_guide.htm