A Thai court has sentenced 15 members of the Red Shirt political movement to four years in prison for inciting rioting that disrupted a regional conference in 2009, a lawyer has said.

The sentencing by a court in Pattaya on Thursday is the latest blow against supporters of the former prime minister Thaksin Shinawatra, who was ousted by a military coup in 2006 after being accused of corruption and disrespect for the king.

Those sentenced included two of the group’s more senior leaders, Worachai Hema, a former pro-Thaksin lawmaker, and Arisman Pongruangrong, a popular former pop singer turned activist, their lawyer Karom Polpornklang said on Friday. Two of the 15 were absent for the sentencing and the others were held after an initial denial of bail.

“The accused were found guilty on multiple charges, including causing unrest, leading more than 10 people to do or threaten to do an act of violence, and trespassing,” Karom told the Associated Press. “We are hoping to bail them out as soon as we can.”

The disrupted meeting was a summit of leaders from the Association of Southeast Asian Nations (Asean), some of whom were evacuated by helicopter after Red Shirts broke into the hotel hosting the conference. The protesters, numbering about 2,000, were demanding that then-prime minister Abhisit Vejjajiva call new elections because they felt he came to office illegitimately after two prime ministers they supported were forced out under questionable circumstances.

Thaksin and his allies have won every national election since 2001. His sister, Yingluck Shinawatra, was forced from the prime minister’s job in 2014 by a controversial court ruling just before another military coup toppled the government.