Billion Star Express is offering new promotion for new route service for bus from Singapore to Kuala Lumpur, Seremban, Penang starting from 11-November-2013. The fare price is from SGD20.
Billion Express has been operating express bus services since 2012. Their most famous routes are bus from Singapore (sg) to Kuala Lumpur, One Utama and Penang. The promotion of price is until end of 2013. The price may vary during the peak season.
BusOnlineTicket.com 
How much for return trip from sg to kl. And also terms and conditions for the discount
Hi Sean, it is $30 for one way