Tyrell Haberkorn, a professor at the Australian National University in Canberra who has written extensively on violence against activists in Thailand, notes that environmentalists who fight business projects backed by the government have been facing threats since the 1970s. But “how blatant the violence has been,” she says, has varied over time.

Sometimes, prosecutors are able to establish clear linkages between the perpetrators of violence and business interests. That was the case in the death of Prajob Nao-opas, the village leader who had exposed toxic dumping by a local company. The 43-year-old knew he was at risk. According to one local media report, he had purchased two handguns to defend himself. But he was shot in broad daylight at an auto mechanic’s shop in February 2013. He died on the way to the hospital.

The man sentenced to death in the case, Phuthorn Kaweepun, was not only an official with the state Department of Industrial Works, he was also the owner of Fusion Development Company, the business that Prajob had accused of toxic dumping. After Prajob’s death, other local residents continued the campaign, took to the courts and were able to force an end to the dumping.

More often, however, activists struggle with a lack of evidence. That’s been the case for Pachern Ketkaew in Bo Nok. He was sitting in front of the small shop he runs with his wife at about 6 pm on Jan. 31, 2011, when a man with a 9 mm pistol jumped out of an approaching car and started firing at him. The bullets missed their mark, but injured two customers sitting nearby.

Pachern recalls sprinting into the woods behind the shop with the gunman in pursuit. Another man, brandishing an M-16, sprayed the store with bullets. The gunmen then quickly turned and fled the scene. Pachern called another activist, Korn-um Pongroi, who hurried to the shop and took him to Jintana’s house, where he stayed for two months.

In Pachern’s mind, there was little question why he had been targeted: He had formed an organization to fight plans to build a trash-burning power plant nearby, and he had also lodged complaints against toxic dumping in the area. “I didn’t want this town to be dirty with garbage,” he says. “I never thought the investors would try to kill me.”

Pachern says the police identified a suspect but never arrested him. The activist says he thinks he knows the identity of the gunmen — he just can’t prove it. Pachern is reluctant to criticize the authorities’ handling of his case, and says the police blame him for putting himself in this position. It's a common complaint in Thailand: that law enforcement authorities are often complacent at best, and complicit at worst.