Thai news reports say 15 members of the "Red Shirt" political movement have been sentenced to four years in prison for rioting that disrupted an important regional conference in 2009.

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

Thaksin and his allies have won every national election since 2001. His sister, Yingluck Shinawatra, was forced from the prime minister's job last year by a controversial court ruling just before another military coup toppled the government. Thaksin's supporters believe the royalist establishment fears his popularity and is attempting to reduce his influence.