The Criminal Court on Thursday sentenced six leaders of the People's Alliance for Democracy (PAD) each to two years in prison for leading followers to seize and then occupy Government House for over three months in 2008.
The PAD leaders are: Chamlong Srimuang, Sonthi Limthongkul, Pibhop Dhongchai, Somkiat Pongpaibul, Somsak Kosaisuk and Suriyasai Katasila.
Public prosecutors had charged them with trespassing on Government House and causing damage to the property from Aug 26 to Dec 3, 2008.
The six were key figures leading PAD protests to pressure then-prime ministers Samak Sundaravej and Somchai Wongsawat to resign, accusing them of conflicts of interest through links with former prime minister Thaksin Shinawatra.
The Criminal Court dismissed the defendants' claim they had nothing to do with the seizure of Government House and had, in fact, urged the protesters not to damage the property.
The court ruled the seizure of Government House was not a peaceful demonstration, as allowed by the then constitution, and that it had affected the rights of other people.
It reduced its initial sentence of three years in prison to two years because the men's testimonies were deemed useful.
Lawyer Suwat Apaipak applied for his clients' temporary release on bail pending appeal, offering 200,000 baht surety for each. The court later approved bail, setting the condition they must not travel outside the country.
Sondhi and dozens of other PAD supporters also face terrorism charges over the occupation of Bangkok's main airports in 2008, which stranded thousands of tourists.
Both yellow shirt leaders and their opponents in the Shinawatra camp have faced a slew of lengthy court proceedings both before and after the junta took over last May.