I would recommend strongly against travelling overland thru northern Malaysia and Soutern Thailand. There is daily unrest with frequent murders of soldiers, teachers and other innocents by "seperatist rebels" This week alone 2 soldiers kidnapped, tourtured and murdered in broad daylight and today 4 soldiers gunned down as well as another teacher. So far this violence has been limited to the extreme south of Thailand. A better plan would be to fly from K.L. to Phuket, Air Asia flys this route very cheaply, and go overland to Samui. I am no chicken little and spend a great deal of time in Thailand and I know of no one who would consider travel through Sothern Thailand right now.
Pgrin