Protest leader Suthep Thaugsuban has called another mass protest for this Sunday to pressure caretaker Prime Minister Yingluck Shinawatra to step down.
The rally is scheduled ahead of the party-list candidacy registration, which opens on Monday at the Thai-Japanese sports stadium in the Din Daeng area.
The announcement came hours after the prime minister yesterday reaffirmed that she would not quit.
Mr Suthep also asked female protesters to be prepared to a join a separate march on Sunday night to the prime minister's residence "to ask her to leave the post nicely".
"We will need female volunteers. Women only. No katoey [transvestites] please. This is between women. The women will give flowers to Ms Yingluck and ask her to have some pride and resign," he said.
According to Mr Suthep, he will have two "rehearsals" before the Sunday rally. On Dec 19, he will march from Ratchadamnoen to the Sukhumvit area via Phetchaburi and Asok. On Dec 20, he will march from the protest venue to Silom via Yaowarat. Saturday will be a rest day.
To ensure a show of force, Mr Suthep urged all local administrative organisations to provide amenities and refreshments for those travelling from the provinces.
He suggested that the demonstrators travel during daylight for safety and prepare for possible blockades by police.
Mr Suthep said that he will not quit until Ms Yingluck vacates the post.
According to Mr Suthep, the People's Democratic Reform Committee (PDRC) has asked diplomats from various countries to observe the Ratchadamnoen protest this afternoon.
He said he will explain the PDRC's "reforms before elections" demand and ask the diplomats to visit the Dhamma Army and the Network of Students and People for Thailand's Reform protest sites.