The protests, however, have escalated into a wider campaign to bring down the government. Separate demonstrations by pro-government groups have raised concerns of clashes.
Opponents of the bill, led by the opposition Democrat Party, vowed late Monday to continue their campaign.
"We will escalate our fight by inviting the people to rigorously carry out civil disobedience throughout the country," Democrat deputy leader Suthep Thaugsuban said.
He called for a three-day closure of businesses and schools to allow people to join the strike; a withholding of taxes that allegedly are used for corruption; the display of the national flag; and the blowing of whistles, which have become a noisy tool of protest, near government leaders.
Suthep, a former deputy prime minister, and eight other party lawmakers resigned their parliamentary seats Tuesday to lead the anti-government campaign. The resignations are a legal shield for the party, which could face dissolution if its lawmakers were found guilty of trying to unlawfully unseat a constitutional government.
Thailand has been rocked by years of often-violent political conflicts that led to Thaksin's ouster, which followed widespread demonstrations against him in Bangkok.
Disputes between Thaksin's supporters and opponents arouse fierce passions which culminated in a 2010 military crackdown on his supporters that left about 90 people dead.
Although the latest protests are the strongest against Yingluck's government, it is unclear if they are sustainable, especially in view of the overwhelming support that her government has in Parliament.
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Associated Press writer Jocelyn Gecker contributed to this report.