Suthep Thaugsuban and government ministers were among former People's Democratic Reform Committee (PDRC) leaders sentenced to jail on Wednesday for their roles in protests against the Yingluck Shinawatra government.
The Criminal Court sentenced Suthep to five years in jail for leading PDRC rallies that paralysed Bangkok and led to turbulence in 2013 and 2014.
Prison sentences were also handed to Education Minister Nataphol Teepsuwan (6 years and 16 months) and Deputy Transport Minister Thaworn Senniam (4 years).
The Constitution bars anyone who has been sentenced to jail from taking political office, meaning a Cabinet reshuffle may now be necessary.
Meanwhile Buddhipongse Punnakanta, former digital economy and society minister, was sentenced to seven years in jail.
He was among a total of 29 former PDRC members who were handed jail terms ranging from four months to 11 years after being found guilty of terrorism, insurrection or other charges.
Chaos caused by the PDRC protests culminated in a coup led by then-Army chief Prayut Chan-o-cha on May 22, 2014.