BANGKOK: Thailand's junta chief on Tuesday ordered an investigation into the shooting of a prominent youth activist by soldiers, as public outrage snowballs over his killing.
Chaiyaphum Pasae, a campaigner for stateless communities in Thailand's border regions, was shot dead on Friday morning in northern Chiang Mai province after the car he was in was stopped at a military checkpoint.
The army says soldiers found drugs inside the car and opened fire after Chaiyaphum bolted from the vehicle and threatened to throw a grenade at them.
But his friends have taken to social media to say that narrative does not chime with the behaviour of an activist renowned for his community campaigns against drugs, who worked on documentaries, music and talks on rights for minority tribal groups -- such as his Lahu people.
"I have ordered an investigation into the cause of this incident," Prime Minister Prayut Chan-O-Cha, a former army chief who seized power in 2014, told reporters on Tuesday, urging the public to refrain from criticising the military.
Rights groups are concerned the military cannot be relied upon to investigate itself.
Advocacy organisation the Cross Cultural Foundation (CCrF) called for the investigation to be conducted by a non-military "commission of inquiry".
It also urged witness protection for a 19-year-old who was also in the car, who has been detained since the incident.
Scores of other activists have died over the last decade in Thailand, where the powerful often lean on local networks to cover-up wrong-doing.
Human Rights Watch said the slaying of Chaiyaphum had "set alarm bells ringing" and urged Thai authorities to "thoroughly and impartially investigate this case and make their findings public".
Chaiyaphum was one of Thailand's stateless citizens -- ethnic groups who have been allowed to stay since the Cold War-era but are denied citizenship, including for their children.
The military described the young activist as a 21-years-old, but friends told Thai media he was in fact 17.
The district where the killing occurred is in northern Thailand near Myanmar, a notorious drug route used by well-armed trafficking groups.
The CCrF believe the military unit who shot Chaiyaphum was involved in another checkpoint killing last month where a similar justification of a suspect trying to throw a grenade at soldiers was given.
Junta spokesman Winthai Suvaree told AFP he was unaware of those claims, but said drug traffickers frequently "resist arrest" in the region where Chaiyaphum died adding the army "doesn't cover them up at all".