The politically-turbulent country has been shaken by weeks of opposition rallies against Prime Minister Yingluck Shinawatra and her divisive former premier brother Thaksin, which have caused the government to call snap February 2 polls.
Demonstrators, who have vowed to disrupt the vote, began packing possessions and equipment at their main Bangkok rally site as they prepared to fan out to seven locations across the city tomorrow in an attempt to choke off transport into the capital.
The protesters want an appointed "people's council" to run the country and oversee vaguely defined electoral reforms before new elections are held in around a year to 18 months.
It is the latest chapter in a saga of political instability and occasional unrest that has gripped Thailand since Thaksin was ousted from power by royalist generals seven years ago.
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Protest leader Suthep Thaugsuban, a former MP for the opposition Democrat party that is boycotting the elections, has said he expects a large turnout for the latest demonstration.
"There will be huge numbers of people from every province joining the shutdown Bangkok mission on Monday 13," he told a rally late yesterday.
The demonstrators say they will block major intersections, stop officials going to work and cut off power to key state offices.
The authorities say they are ready to declare a state of emergency if there is fresh unrest, and roughly 20,000 police and soldiers will be deployed for security.