Sai In-come, head of the rubber farmers' network in Phayao province, said on Sunday that rubber farmers from all regions of the country had come out to ask the government for help.
Farmers in the North and Northeast had submitted a letter to the government in April, asking it to keep prices of raw rubber sheets (grade 3) at 92 to 98 baht per kilogramme and cut lumps at 85 to 87 baht/kg. But five months had passed and the government had yet to lend a hand to the farmers, he said.
"A group of rubber farmers are prepared to gather on Sept 3 but we'll wait for the result of a House meeting on Aug 29 first.
"If we receive proper assistance from the government, the farmers will not block roads. But if we don't receive any help, there'll be protests nationwide," Mr Sai said.
Political parties should not play politics and cause trouble to civilians, he added.
Agriculture and Cooperatives Minister Yukol Limlaemthong said rubber prices are down because the global economy has yet to recover and it is impossible to sell rubber at 120 baht/kg.
"The government is not interfering because it wants rubber prices to move in line with the market mechanism," Mr Yukol said.
He said the government has allocated a budget of 20 billion baht to buy rubber.
There is more than 200,000 tonnes of rubber in stock but it could not be sold at this time, he said.
"If the farmers want the government to buy more rubber or keep prices from falling further, we don't know how much money we'll have to spend," said Mr Yukol, who is also a deputy prime minister.
However, prices of agricultural products, especially animal feed, are expected to slightly increase this year, he said.
On Friday, about 500 rubber and oil palm farmers from Nakhon Si Thammarat and neighbouring provinces blocked off part of Highway No.41 to call on the government to prop up plummeting crop prices. More than 40 people were injured when police tried to disperse them.