There are many buses, every day going from KL to Hat Yai (via the Bukit Kayu Hitam border in Kedah) and Singapore (via the Johor Bahru border in Johor).

The Orange Coach operator is a luxury coach operator that provides daily services from Singapore to KL, and vice versa. There are also Transnasional buses from the major states like Johor Bahru, Melaka and Penang, into KL. These luxury coaches traverse over long distance routes and are equipped with full premium facilities that offer a comfortable and safe journey.

Note that usually you will need to exchange your ticket for a 'boarding pass' before boarding the bus, so it is advised to arrive at your designated bus terminal 10-15 minutes before the departure time.

More Information

Bus Operator list

Bus Company Website
Transnasional Sdn. Bhd http://www.transnasional.com.my/?
SANI Express http://www.saniexpress.com.my/home.html
Plusliner    http://www.plusliner.com.my/
Bumi Express   http://www.spbumi.com.my/Main/Main.asp?pageID=002
CEPAT Express http://www.cepatexpress.com.my/Main/Main.asp?pageID=002
MARA Liner http://www.maraliner.com.my/Main/Main.asp?pageID=002
MAHLIGAI Express http://www.mahligai.com.my/Main/Main.asp?pageID=002
UTAMA Express http://www.utamaexpress.com.my/Main/Main.asp?pageID=002
Darul Naim Express http://www.darulnaimexpress.com.my/Main/Main.asp?pageID=002
Delima Express http://www.delima.com.my/Main/Main.asp?pageID=002
Orange Coach http://www.orangecoach.com.sg/Index.aspx