Disputes between Thaksin's supporters and opponents arouse fierce passions which culminated in a 2010 military crackdown on Thaksin supporters that left about 90 people dead.
Paving the way for Thaksin's return has been an unspoken priority of Yingluck's government, which won an absolute parliamentary majority in 2011 elections due largely to Thaksin's popularity in rural areas and among the urban poor, who benefited from his government's populist programs.
The bill also triggered opposition from the pro-government supporters who wanted to prosecute those behind the killings during the 2010 crackdown.
On Monday evening, Democrat Party lawmakers called for a three-day strike by businesses and schools to allow people to join the protests; a withholding of taxes that allegedly go for corruption; the display of the national flag; and the blowing of whistles, which have become a tool of protest, near government leaders.
Democrat lawmaker and former Deputy Prime Minisiter Suthep Thaugsuban, along with eight other party lawmakers, said they were resigning their parliamentary seats 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.
Although the protests have drawn a high profile and are the strongest ever against Yingluck's government, it was unclear if they are sustainable, especially in view of the overwhelming support Yingluck's government has in Parliament.
The original draft of the bill did not extend amnesty to the leaders of both the pro- and anti-Thaksin groups, but a House committee in mid-October suddenly changed the bill to include both. The last-minute change led to criticism that it was planned all along to encompass Thaksin.
"If Mr. Thaksin and other leaders had not been added to the amnesty bill coverage, the majority of the people would have agreed to give amnesty to the ordinary people affected (in the conflict)," said Prinya Thaewanarumitkul, a law professor at Bangkok's Thammasat University.