Tension was renewed over the weekend in southern provinces after farmers declined the government's offer to subsidize rubber prices.
Last week, the Cabinet approved a 21.2 billion baht ($657 million) program for the farmers but it was never formally accepted by some farmers' representatives who threatened to take a more hard-line stand in their demands, include shutting down a port, a border checkpoint and a major road junction in the south, where most of the country's rubber is grown.
The disruptive but generally peaceful protests turned violent two weeks ago, in one case leaving more than 20 police officers injured after bricks and bottles were hurled at them.
Thailand is the world's top producer and exporter of natural rubber, which is used in products from condoms to car tires. Due to weaker demand in a sluggish global economy, prices for rubber have steadily dropped since peaking in 2011.