Thailand has seen its second mass killing in two months linked to the country's embattled network of village chiefs. Prathuang Ruanhaew, 37, an assistant to a village headman in Baan Kwang, north of Bangkok, ran amok on Sunday with a pump-action shotgun, killing four neighbours and then shooting himself dead. Relatives and friends said he had suffered a nervous breakdown following mounting work pressure. His parents had grown alarmed at his condition and had planned to take him to hospital this week. The deaths follow the shotgun killing of six district officials during a meeting in November when headman Veera Jitjantuk sought to clear his name over corruption allegations. Veera has since been arrested but has yet to come to trial. Once well-respected leaders given powerful community administration roles for life, many headmen - or kamman - had degenerated into mafia-style chiefs, controlling all manner of legal and illegal businesses during Thailand's boom. Concern at their omnipotent role in rural life reached a peak last year, and a new constitution, signed into law by King Bhumibol Adulyadej last October, is set to wipe away much of their power. They will have to work with professional administrators, will lose their right to hold the job for life and will face regular elections. How successfully the kamman can be controlled will be a key early test of the document hailed as the 'people's charter'.