Red-shirts from Nakhon Ratchasima province on Monday announced they would join their colleagues at a protest rally against Constitution Court judges in Bangkok on Wednesday.
Sompote Prasartthai, a red-shirt leader in Muang district, said all red-shirt leaders of the United Front for Democracy against Dictatorship (UDD) in 32 districts of the northeastern province were mobilising protesters and organising transport for the trip.
As of Monday, at least a thousand people were expected to attend the protest led by the "group of people's radio media for democracy", which is in its 14th day, he said.
The protesters will travel to the rally site in front of the Constitution Court, which is headquartered in a building of the government complex on Chaeng Wattana Road, by charter buses, vans and private cars, he said.
Mr Sompote said the protest would be peaceful and would not cause problems for people in Bangkok.
The organisers of the protest set May 8 for a mass gathering and called on red-shirts across the country to join them, to increase pressure on the nine charter court judges to resign.
Deputy metropolitan police chief Parinya Chansuriya on Monday called a meeting to discuss preparations for Wednesday's mass rally.
Pol Maj Gen Parinya said there were about 2,000 protesters at the rally site on Sunday evening. Most of them returned to their homes about midnight.
There would be no increase in the number of police assigned to the rally because of the limited space on the premises, but backup units would be ready for immediate deployment if needed, Pol Maj Gen Parinya said.