MEKONG RIVER • The Myanmar-Laos border, which the Mekong delineates, is mostly unguarded.
The terrain is rugged and hostile, with rebel armies holding sway in some areas and the drug industry flourishing in lawless enclaves on both sides of the river.
Regional law enforcement agencies are often underfunded and ill-trained, and the intelligence they gather is not effectively shared with neighbouring countries.
In October 2011, a gang led by a Mekong pirate called Naw Kham murdered 13 Chinese sailors. He was hunted down in Laos, then taken back to China to be tried and executed.
Afterwards, Chinese gunboats began patrolling further downriver, extending China's security reach far beyond its borders. This includes a riverside facility in Muang Mom in Laos, which Reuters visited. It is run and guarded by a 25-strong unit of Chinese People's Armed Police.
China conducts monthly joint patrols with its Laotian and Myanmar counterparts.
In 2013, a Chinese-Laotian patrol found 580kg of methamphetamine pills, worth more than 100 million yuan (S$21 million), hidden in a cargo ship.
Besides increasing patrols, Mekong countries also need to coordinate and share intelligence to interdict more drugs, said Mr Jeremy Douglas, the Asia-Pacific chief of the United Nations Office on Drugs and Crime.
Some areas remain intelligence black holes controlled by heavily armed rebels, added Mr Douglas, although he hoped Ms Aung San Suu Kyi's new government would engage with them and secure better access to them.
The ever-shifting river created islands, where drug shipments were hidden, said Colonel Patpong Ngasantheir of the Royal Thai Army.
But according to a treaty negotiated while Laos was still a French colony, these islands are deemed neutral.
"We're not allowed to search them," he said.