World Bulletin/News Desk

Thailand's "red shirts" took to the street this weekend to mark the anniversary of the army's bloody repression of their mass rally in Bangkok in 2010 amid growing signs of a rift with the government they helped elect last July.

Many red shirts are angry at the failure of Prime Minister Yingluck Shinawatra to bring to account those responsible for the 91 deaths during the 2010 events. Some are threatening action that could destabilise her government and start another period of political upheaval, after months of relative calm.

At least 20,000 people attended the rally, which ended peacefully in the early hours of Sunday. They blocked a major crossroads where a huge shopping mall was set on fire during the dispersal of the 2010 rally.

"My son has been in prison for two years and hasn't been allowed bail. I haven't received any help from this government to get him out," said Bantao Muangkot, whose son was arrested for allegedly setting fire to a town hall in the northeast.

Families of those killed fear a political amnesty bill proposed by the Yingluck government could see charges dropped against those guilty of crimes related to Thailand's six-year political crisis, including members of the military, former ministers now in opposition and ex-premier Thaksin Shinawatra.

Red shirts at the rally held pictures of Thaksin, Yingluck's brother, who was ousted in a coup in 2006. He has chosen exile to avoid going to jail after being found guilty of a conflict of interest when he was in power but is itching to return.

Though they support Thaksin, many red shirts are demanding a full investigation into the military's role in the deaths.

"Most red shirts I spoke to said that if they were forced to choose, they would rather see those responsible for the violence go to jail than bring Thaksin home to Thailand," Thida Thawornseth, leader of the red shirts' United Front for Democracy Against Dictatorship, told Reuters.

Thaksin addressed the rally through a video link.

"I know you feel hurt, but we have to push personal issues to one side and work for the greater good, for reconciliation," he told the crowd. "Those responsible for the killings in 2010 will be brought to justice but that could take some time."

The government has enjoyed an uneasy peace since taking office, facing little opposition from the royalist, anti-Thaksin "yellow shirts" of the People's Alliance for Democracy, whose leaders also stand to gain from an amnesty, having organised the invasion and closure of Bangkok's two airports in 2008.

Natthaputt Akhard, whose sister, Katekamol, a volunteer nurse, was shot dead in a temple during the crackdown on the 2010 rally fears most cases will remain unresolved.

"My mother whispered to Thaksin at a red shirt gathering in Cambodia that she didn't want an amnesty deal, she wanted the truth," said Natthaputt.

Soon after, Thaksin addressed red shirts on Thai television, asking them to "make sacrifices" for the greater good.

"Thaksin would be betraying the reds if he made a deal at their expense," said Thitinan Pongsudhirak, a political analyst at Bangkok's Chulalongkorn University.

Anger at the government's refusal to amend Thailand's strict laws that shield the country's monarchy from criticism is also causing tension. Many red shirt supporters at the rally wore T-shirts calling for an amendment to the lese-majeste laws.

That is a sensitive issue in a country where King Bhumibol Adulyadej is regarded by many as semi-divine.

Critics say the laws are being abused to silence or imprison opponents of the royalist establishment and some are angry that Thaksin and Yingluck seem more interested in reaching a political compromise than addressing injustice.

"This government should try harder, especially to ensure red shirts still in jail are treated in a humane way," Thida said.