Protesters throw shoes at Thai PM
The protesters refuse to give up until Mr Somchai and his government resign
Angry protesters have thrown shoes and bottles at Thailand's Prime Minister Somchai Wongsawat.
About 200 state employees surrounded his car outside the Information Ministry, and called him a murderer.
Mr Somchai is under pressure to resign over recent clashes between police and an anti-government group.
Protesters also say he is too close to former PM Thaksin Shinawatra, who was sentenced to two years in jail on Tuesday for violating corruption laws.
Thai prosecutors have now begun to gather evidence to submit to the UK, where Thaksin currently lives in self-imposed exile, asking for his extradition.
Protesters from the People's Alliance for Democracy (PAD) have been camping outside Government House for two months now, calling for the government to be disbanded and a partly appointed administration put in its place.
The continuing demonstrations are virtually paralysing Mr Somchai's administration.
Repeated attempts to move the protesters have failed, and the government has been forced to operate from a disused airport.
Thai prosecutors are gathering evidence to try to extradite Thaksin
The demonstrations began peacefully, but there were violent clashes between police and protesters earlier this month, and the country's army commander has backed calls for Mr Somchai to step down to take responsibility for what happened. But Mr Somchai has only been in his post for a month, and despite Wednesday's attack, he is standing firm.
"This morning was a bit colourful, but I have to work and I am not worried about these things - people can have different opinions," Mr Somchai told the French news agency AFP.
"It would not be a problem for me to resign, but what will people get from my departure?... I cannot stop working otherwise government development projects would be halted."
On Tuesday Thailand's Supreme Court found Thaksin guilty of corruption and sentenced him to two years in jail in absentia.
In a landmark ruling, he was found to have violated conflict of interest rules in helping his wife buy land from a state agency at a knock-down price.
Prosecutors are now gathering evidence to submit to the UK.
"The extradition process began today [Wednesday]," said Sirisak Tiyapan, international affairs director at the attorney general's office.
"All documents must be translated into English before we can prepare the petition and that will take considerable time," he told the AFP news agency.
"In our petition, we have to prove Thaksin committed a crime that is common between the two countries."
After the ruling, the PAD said the court's decision had vindicated the protesters' actions.
"The verdict meant our campaign against Thaksin was right all along, which will bring more people to join our campaign now to bring him back home to serve his sentence," PAD leader Suriyasai Katasila told Reuters news agency.