Companies acquired concessions amounting to the size of a small European country, while rural residents of Southeast Asia’s Mekong region saw their landholdings shrink or disappear over the past two decades, according to researchers.

Demand for sex with children is an emerging cause of human trafficking in the Mekong region, the United Nations said on Thursday, as it pointed to a shift in child sex webcam centres from the Philippines to Thailand.

China’s plan to blast open more of the Mekong River for bigger cargo ships could founder on a remote outcrop of half-submerged rocks that Thai protesters have vowed to protect against Beijing’s economic expansion in Southeast Asia.

A rainbow-headed snake and a dragon-like lizard are among 163 new species that scientists recently discovered in the Greater Mekong region, conservation group WWF said on Monday, adding rapid development in the area, from dams to mines, was threatening wildlife survival.

Conservationists called on the Mekong nations to follow in Vietnam's footsteps, after Hanoi destroyed tonnes of illegal ivory over the weekend.

Thailand's Prime Minister Prayuth Chan-o-cha says a new action film about the massacre of Chinese sailors on the Mekong River in 2011 will be banned if it is found to "damage" the country.