The farmers had asked the government to buy raw rubber sheet at 92 baht per kilogramme, latex at 81 baht/kg, rubber scrap at 83 baht/kg and smoked raw rubber sheet at 101 baht/kg.
However, Agriculture and Cooperatives Minister Yukol Limlaemthong insisted that raw rubber sheet would be bought at 80 baht/kg and that the government will not intervene in the rubber market.
The rubber farmers' representatives walked out of the meeting immediately after Mr Yukol made the statement, and said a mass protest and road blocks will definitely take place on Sept 3 because the government did not care about the farmers facing hardship.
Meanwhile, the rubber farmers' protest in Nakhon Si Thammrat province entered its sixth day on Wednesday, with the leaders intent on guarding their rally sites to prevent riot police dispersing them.
Trucks remain parked across the main southern highway, blocking all lanes, and the railway tracks between Ban Toon and Cha-uat railway stations in Cha-uat district, as planters demanded the government guarantee a higher price for their sheet rubber. They demanded to know why the government was favouring rice farmers with heavy subsidies.
Somporn Yodrabum, one of the protest leaders, said the government should avoid using force against them and should settle the dispute through negotiation.
"If force is used to break up the protest the situation will certainly escalate," Mr Somporn said.
Reports said the protesting farmers had also planned to block a main road in Nakhon Si Thammarat's Chian Yai district on Tuesday night but were foiled when 500 police were deployed there ahead of them.
Agriculture and Cooperatives Minister Yukol Limlaemthong, also a deputy prime minister, said the farmers have the right to protest but must stay within the law.
"We'll have to explain the rubber price situation to the farmers.
"The government is not passive about helping farmers, whether or not they're in the South. The government is ready to help, regardless of what political party they support," Mr Yukol said.
The South is the political stronghold of the opposition Democrat Party.
Meanwhile, corn farmers in Phetchabun plan to join the rubber farmers' protest and block roads across the country on Sept 3 if the government fails to give a clear answer to tackle tumbling maize prices.
Pin Wangsampao, a representative of corn farmers in Phetchabun, said he had submitted a letter to provincial governor Jirayuth Watchanarat, asking the government to intervene in the maize prices. However, the cabinet meeting on Tuesday did not consider the issue, causing corn farmers to feel uncertain.
"If the government fails to give an answer on Thursday we're ready to put on pressure by blocking roads with the rubber farmers nationwide on Sept 3," Mr Pin said.
He said corn farmers had already finished harvesting and the cost of damage could increase if the government failed to act promptly. Traders were now pressing farmers to sell their corn at only 5.60 baht per kilogramme, he added.
According to an agreement between corn farmers and the Internal Trade Department, corn with a humidity level of 14.5% is sold at nine baht/kg while corn with a 30% humidity level is sold at seven baht/kg.