Lt Col Yi Se, leader of an ethnic Lahu guerrilla group operating in Myanmar's Shan state, died at the age of 78 on Wednesday night, according to a source familiar with Thai-Myanmar border affairs.
Lt Col Yi Se: Led militia for 30 years
The source, who works in Chiang Rai province on this side of the Thai border, said under Lt Col Yi Se's leadership, the militia became notorious for its suspected involvement in transborder drug smuggling in northern Thailand.
Lt Col Yi Se was pronounced dead at about 6pm in a hospital in Shan's Mong Hsat district from what are believed to be natural causes, the source said.
The body was transferred from the hospital to a village in the same district for a Christian funeral, the source said, adding the village is located just opposite Mhong Kao Lang village in Chiang Rai's Mae Fa Luang district.
Lt Col Yi Se served for more than 30 years as the leader of the militia, the source said.
He formed an alliance with Myanmar's junta after breaking away from the Mong Tai Army (MTA), an insurgent group led by the late ethnic Chinese drug lord Khun Sa, also known as Zhang Qifu, the source said.
Founded in 1985, the MTA consisted of members of the Shan minority. It was dissolved in 1996.
It reportedly had up to 20,000 armed insurgents at its peak, considered one of the largest forces opposing the junta at the time.
The group faced accusations of drug trafficking in the region.
Lt Col Yi Se's militia was believed to have worked with drug manufacturing gangs in Wa state, smuggling narcotics into Chiang Rai's Mae Fa Luang and Mae Sai districts, the same source said.