Police spokesman Piya Uthayo said demonstrations are expected in Krabi, Trang and Surat Thani, adding to ongoing protests in Nakhon Si Thammarat and Chumphon.
The focus of Tuesday's protests is likely to be in Surat Thani's Phunphin district, where up to 5,000 farmers are expected to gather and call on the government to stabilise rubber prices, Pol Maj Gen Piya said.
The two other protests, which will be organised outside the provincial halls in Trang and Krabi, are likely to draw around 300 protesters each, he added.
Pol Maj Gen Piya said national police chief Adul Saengsingkaew had instructed provincial police commanders to work with their respective governors and attempt to dissuade protesters from blocking roads or rail lines.
Surat Thani police commander Kiattipong Khaosam-ang said about 1,300 officers from Surat Thani, Phuket and Krabi will be deployed to maintain order at the rallies.
He said authorities will avoid action that might provoke the protesters.
Police will set up seven checkpoints to keep drugs and weapons out of the rallies, he said.
Provincial authorities are also placing fire engines and reserve power sources on standby in case they are needed.
Protests by rubber farmers in the region have intensified since they began last week, with 2,000 rubber and palm farmers rallying yesterday outside Chumphon provincial hall to demand the government subsidise falling prices.
The protesters, most of whom are from Chumphon and neighbouring Prachuap Khiri Khan, demanded the government guarantee the price of smoked rubber at 101 baht/kg, the price of unsmoked rubber sheet at 93 baht/kg, latex at 82 baht/kg, and palm at six baht/kg.
They have threatened to intensify their protests if the government fails to take action by today.
Rubber farmer representative Somkid Chaiwat said the government's proposed measures to deal with the farmers' concerns had drawn mixed reactions.
The government has proposed a subsidy of 1,260 baht per rai of rubber plantation, limited at 10 rai per farmer. It has also offered to raise the raw sheet rubber price to 80 baht/kg.
Mr Somkid said some farmers wanted the government to increase the subsidy cap to 25 rai.
Many farmers do not own their rubber plantations and therefore would not be eligible for the state subsidy, he added.
Deputy Prime Minister Kittiratt Na-Ranong said the cabinet on Tuesday will approve the per-rai subsidy to ease the impact of falling rubber prices.
He said the government would hold talks with protest leaders tomorrow to discuss their other demands, and their proposals will be submitted to the national rubber policy committee on Thursday.
He said the government would keep the door open for talks.
Prime Minister Yingluck Shinawatra expressed concern about Tuesday's protests but insisted there was no need to impose the Internal Security Act to control the situation.
She rejected the farmers' demands, asking the protesters to understand that the government could not buy rubber at the prices demanded.
Meanwhile, the government said yesterday the shooting of rubber protesters in Nakhon Si Thammarat's Cha-uat district on Sunday stemmed from a personal quarrel.
A security guard was killed and one protester was wounded in the attack.
Deputy Prime Minister Pracha Promnok said gunshot residue found on the wounded man indicated he was shot at close range.
According to witness accounts, a quarrel took place before the shooting. The two men were shot from a distance of about half a metre, Pol Gen Pracha said.
Nobody from outside was believed to have been involved in the shooting because the protesters were well guarded and security around the venue was tight, he said.
Earlier reports said a group of armed men opened fire on protesters at Ban Toon railway crossing early on Sunday morning.
Pol Gen Pracha said he believed police were planning to seek an arrest warrant for the shooting suspects.
Iad Seng-iad, a protest coordinator in Cha-uat, said the demonstrators would stay put as rubber farmers in other provinces proceed with their protests today.
Meanwhile, in the North and Northeast, farmer leader Pongnimit Kaewdaeng said his network would give the government until Sept 13 to implement its proposed measures.