This came as anti-government protesters resumed marches in Bangkok, trying to energise supporters in the centre of the Thai capital before a planned weekend rally to put pressure on Yingluck to step down.

Yingluck called a snap election last week when the protests reached their height. She remains caretaker premier until the vote, but has refused to push back the date to allow the drawing up of political reforms demanded by the protesters.

"Once the government has resigned, I would like to have other people who are neutral take charge," said protester Siriroj Oh-Prechacharn as marchers prepared to leave the main rally site at Democracy Monument.

About 160,000 protesters surrounded Yingluck's office on December 9, but momentum has waned since then. The National Security Council said there were about 3,000 people at yesterday's march, about half as many as were there when the latest round of marches began on Thursday.

The registration of political parties begins on Monday, with attention focused on whether the main opposition Democrat Party will decide to take part.

Democrat lawmakers resigned from parliament this month to march with protest leader Suthep Thaugsuban, who was deputy prime minister in a Democrat-led government until 2011.

Some agree with his call for reforms to be implemented before another election is held, but others believe their party, Thailand's oldest, should respect the democratic process and run for office. The party's decision is due to be announced today.

A boycott would damage the credibility of the vote and prolong uncertainty.

Suthep says the election should be postponed until reforms are implemented by a "people's council" his movement will have a say in nominating.