The ongoing anti-drug campaign is not the first time the four countries have cooperated to prevent crime on the Mekong River.

Police forces set up joint patrols after hijackers killed 13 Chinese sailors on two cargo ships in a Thai section of the waterway on Oct 5, 2011.

At Guanlei Port in Yunnan province's Xishuangbanna Dai autonomous prefecture on Friday, Chinese officers were scheduled to leave on three vessels to join counterparts from Laos for the 10th patrol mission, due to last three to four days.