Thai protesters have besieged several more government ministries as part of their efforts to topple Prime Minister Yingluck Shinawatra.
Demonstrators have surrounded the interior, agriculture, transport, and sports and tourism ministries, ordering officials inside to leave, a day after occupying the finance and foreign ministries.
Protest leaders said the demonstrations would spread, raising the risk of violence after a tough security law was imposed across Bangkok late on Monday to control the rallies.
Tens of thousands of demonstrators have rallied against Ms Yingluck and her brother, ousted premier Thaksin Shinawatra, in the biggest street protests since 2010.
Ms Yingluck has reiterated a vow that authorities would "absolutely not use violence".
"Everybody must obey the law and not use mob rule to upstage the rule of law," she told reporters.
Police numbers have been increased in Bangkok in response to the expansion of the Internal Security Act, which gives authorities additional powers to block routes, impose a curfew, ban gatherings and carry out searches.
MPs began debating a no-confidence motion on Tuesday, which was put forward by the opposition Democrat Party last week as part of a barrage of legal and institutional challenges to the government.
The ruling Puea Thai party holds a comfortable majority in Parliament and is expected to win a censure vote.
The recent protests were sparked by the government's plans to introduce an amnesty that could have allowed the return of Mr Thaksin, who was ousted in a 2006 coup and lives in self-imposed exile.
Outrage over that plan failed to ebb after the amnesty bill was quashed by the Senate on November 11.
The Finance Ministry is still functioning well despite being occupied by protesters, minister Kittirat Na Ranong said.
"There will be no impact on the fiscal budget and important functions," he said.
However, Mr Kittirat says the economy will be affected in the current quarter if the situation continues.
He says the ministry will file a lawsuit against protest leader Suthep Thaugsuban and investigate ministry officials who had facilitated the invasion.
Mr Suthep, a former deputy prime minister in the previous Democrat-led government, says he would welcome any police or soldiers who wanted to join his campaign.
"We hope that this time it will be a movement of the people to temporarily take hold of the governance of this country," he said.
"If the police or military join us, we welcome them. But they will have to listen to the people."
Her broad support in Thailand's vote-rich rural north and northeast helped her win a 2011 election by a landslide, making her Thailand's first woman prime minister.