From what began as peaceful street protests against the powerful Thaksin Shinawatra government in 2006, the now-defunct yellow-shirt People's Alliance for Democracy (PAD) movement got out of control in the following years. It leaders then resorted to extremism and violence, sexed up by hate speech.
Their actions, such as the invasion of government offices and airports, have become the prototypes of violent and lawless tactics adopted by other protest groups during the past decade.
On Wednesday, the Supreme Court upheld the Appeal Court's sentencing of six former PAD leaders to eight months in jail each for the group's seizure of Government House for more than three months in 2008.
Public prosecutors earlier arraigned the six leaders on charges of leading protesters to force their way into Government House, camping in and around the premises and damaging property there during the protests against the Thaksin-linked Samak Sundaravej government.
The Supreme Court ruled that their demonstration was not peaceful as they claimed, and that protesters also damaged a lot of state property.
The six leaders are Maj Gen Chamlong Srimuang, Sondhi Limthongkul, Pibhop Dhongchai, Somkiat Pongpaibul, Somsak Kosaisuk and Suriyasai Katasila.
In addition, the six men and other 92 former PAD leaders faced a criminal case for their shutdowns of Suvarnabhumi and Don Mueang airports in 2008. Earlier, the Civil Court ordered 13 of them to pay 522 million baht in compensation for the temporary airport closures.
These PAD leaders may not have had to end up in jail or be forced to pay huge fines if they had not led and incited the protesters to break the law and threaten the safety of public and government officials.
In its effort to pressure the former governments linked to Thaksin, the group set up armed and unarmed forces who mingled among protesters as "PAD guards" and used tens of thousands of their protesters as human shields against the police crackdown.
The PAD's ruthless operations brought about the arrival of its opponent, the red-shirt United Front for Democracy against Dictatorship (UDD), which adopted similar tactics even though they were not as extreme as those of the yellow shirts.
A faction of the UDD in 2009 stormed the Asean Summit in Pattaya, forcing the cancellation of the meeting. The court in 2015 handed a four-year jail term to each of 15 UDD leaders.
The People's Democratic Reform Committee (PDRC), an offshoot of the PAD supporters, followed this by organising street protests in 2013-2014 that culminated in the "Bangkok shutdown", with the occupation of many government buildings throughout the capital.
These countless unlawful and violent acts, led by those who have sowed hatred and distrust among Thais, not only led to deaths and injuries but also economic damage.
Street demonstrations must be allowed for citizens to air their grievances, demand justice, and call for political and social change, among other things.
The mayhem that broke out is understandable. But protests that resort to violence and lawless tactics as they aim to shut down government offices or major public services and compromise the safety of individuals cannot be tolerated.