Chaiwat Sinsuwong, a leader of the group, said the mass rally would begin at 5pm and continue until the government agreed to step down.
A few hundred Thai Patriotic Front members have been camping in Sanam Luang since May 7, despite an order by the Bangkok Metropolitan Administration (BMA) to move to another rally site.
However, Chaiwat insisted Friday that his group would continue the rally at Sanam Luang because they were invoking their constitutional rights to demonstrate.
The Nation