More than 20 environmentalists and human rights defenders have been killed in Thailand since 2001, and few of those responsible have been held to account.
A gunman riding pillion on a motorcycle shot 47-year-old Thongnak nine times in front of his house in Samut Sakhon province's Muang district at about 10am on July 28, witnesses told Human Rights Watch.
Thongnak was hit with 9mm bullets in his left shoulder, abdomen, chest, and back, and died shortly after he arrived at a hospital.
''The government does little to recognise the contributions of environmentalists and human rights activists, then does even less after they are mowed down,'' said Brad Adams, Asia director at Human Rights Watch.
''The Thai authorities need to get to the bottom of Thongnak's killing and hold accountable those responsible for the violence that stalks activists.''
Earlier in July, Thongnak filed a complaint with the Muang district police station in Samut Sakhon province that he had received anonymous telephone calls threatening him with death if he continued to protest against the coal industry in the province.
Only after his murder did the Samut Sakhon provincial governor finally order police to provide protection to Thongnak's family and other members of his network.
Over the past five years, Thongnak led villagers in Muang, Ban Phaeo, and Krathum Baen districts in high-profile protests against the persistent problem of air pollution from dust and fumes from coal depots and separation factories.
On July 13, he led approximately 1000 protesters in a demonstration on Rama 2 Road in Samut Sakhon province for several hours, pressing the provincial governor to sign a memorandum of understanding that the coal depots and separation factories cease operating immediately and the Pollution Control Department step in to inspect those business establishments.
On July 22, he led a group of residents in Tha Sai sub-district of the Muang district, who seized a coal truck, allegedly for violating the Samut Sakhon provincial governor's order banning transportation of coal in and out of the sub-district. Then, on July 26, he testified in an administrative court case against a company that had transported coal into Tha Sai sub-district.
Samut Sakhon province has five authorised coal importers and factories, plus dozens more disguised as ports and warehouses for loading and unloading fishery and agricultural products. Residents contend that these businesses pose a health hazard, but the authorities have permitted the companies to operate without the public hearing and proper environmental assessment in accordance with article 67 of the Thai constitution.
The killing of human rights defenders and other civil society activists has been a serious blot on Thailand's human rights record, Human Rights Watch said.
In line with the United Nations Declaration on Human Rights Defenders, the Thai government should make a commitment to protect people who dedicate themselves to protecting the environment or promoting human rights.
Investigations of these killings have suffered from inconsistent and sometimes shoddy investigatory procedures by the police, the failure to provide adequate protection for witnesses, and the inability to tackle political influence connected to these crimes. Even in serious criminal cases involving the public interest that are referred to the Justice Ministry's Department of Special Investigation (DSI), those responsible are rarely prosecuted.
In major cases involving murdered environmentalists and human rights defenders, the authorities have failed to find those responsible and hold them accountable.
In one such case, a Buddhist monk, Phra Supoj Suwajano, was stabbed to death on June 17, 2005, in connection with his work to protect forests in northern Chiang Mai province from illegal land grabbing.
In another case, a Muslim lawyer, Somchai Neelapaijit, was ''disappeared'' on March 12, 2004, by a group of police officers after he had taken a high-profile role in exposing police torture and other abuses related to counterinsurgency operations in Thailand's southern border provinces.
''The government's response to deadly attacks on environmentalists and human rights defenders has long been inadequate,'' Adams said. '
'This has contributed to an environment that emboldens those who consider using murder to get rid of people who stand in their way.''
For more Human Rights Watch reporting on Thailand, please visit: http://www.hrw.org/en/asia/thailand