The mystery over the fate of Khieu Samphan once again reveals just how elusive the last band of Khmer Rouge rebels are. Thought to be just inside the Cambodian border and down to their last 1,500 fighters, the rebels' ability to move through the jungle cannot be underestimated. On Monday they were blamed for a grenade attack on a casino on the southern coast near Koh Kong, which Thai police said was a bid to get protection money. Thailand could prove crucial if the final squeeze is mounted. A new military broom could take a while to reach the borders where vital contacts are strongest, despite the best will of a Democrat-ruled Bangkok, diplomats fear.