Human Rights Watch is urging the Thai government to prosecute those responsible for killings during last year?s anti-government demonstrations.
The rights organization also said the government is responsible for an ongoing crackdown targeting political opponents as the country heads towards nationwide elections.
It accuses the Thai government of failing to fully investigate last year?s political violence, which it blamed on both the military and opposition protesters.
Last year thousands of anti-government protesters, known as the Red Shirts, occupied Bangkok streets demanding a new election. After a months-long standoff from March to May, the government ordered the military to end the demonstrations. The clashes that followed killed 90 people, most of them civilians.
Brad Adams, the Asia Chief for Human Rights Watch, told a news conference in Bangkok that military snipers appear to have targeted civilians.
"The government cannot simply say that in the heat of attempts to clear demonstrators from the streets of Bangkok, some soldiers may have exceeded their orders," Adams said. "The government provided these orders and the army put these snipers in place and people died."
Adams said the military?s historic impunity is holding back Thailand?s rule of law and democracy.
He added a government appointed truth and reconciliation commission has been ignored by the military and not given enough resources to fully investigate the violence.
Thani Thongphakdi, a spokesman for Thailand's Foreign Ministry, defended the government?s actions.
"The events that occurred were very chaotic," he said. "And, there were a number of cases where it is unclear, both from witnesses account as well as from forensic evidence, as to the people behind the various deaths and injuries. Let me just reiterate that the investigation has not yet closed. It is still ongoing. And, we hope that a conclusion could soon be found," said Thongphakdi.
The Human Rights Watch report also criticized some Red Shirt leaders for the violence. The rights group says some of the leaders publicly welcomed armed elements known as Black Shirts who fought with Thai soldiers.
And, as the military moved in to end the demonstration, Human Rights Watch says some Red Shirt leaders encouraged looting and arson that burned tens of businesses and buildings in downtown Bangkok.
Brad Adams also criticized a government campaign of censoring opponents using laws meant to protect the monarchy from defamation, or Lese Majeste.
"The crackdown on dissent has been ongoing," said Adams. "The government has used any laws at its disposal to stifle speech, it has used the Lese Majeste law in a politically motivated manner, it has targeted one side. We have very large numbers of the Reds who have been arrested for what happened during the protests and we have no one on the government side who has been held accountable," he said.
Thani defended the government's closing down of hundreds of Red Shirt publications, radio stations, and websites since the protest, saying it was done under the rule of law.