The protesters reached an agreement with local officials to reopen the northbound section of the road but to designate one lane for northbound traffic to Bangkok and the other lane for southbound traffic.
The agreement was negotiated by Sommitr Silpraset, the deputy governor of Prachuap Khiri Khan, and Somporn Patchimpech, the district chief of Bang Saphan Noi, the site of the protest.
Provincial officials wanted both sides of the road reopened but the protesters disagreed, so the compromise was reached to allow two-way travel.
However, police rejected the idea because of concern about the safety of road users along the six-kilometre section.
Pol Maj Gen Thanate Sunthornsuk, Commander of Prachuap Khiri Khan police, said the decision was based on an evaluation by officers from Provincial Police Region 7.
The police said they could not guarantee the safety of road users because there was still a protest at Ban Sri Nakhon at the 415km marker in tambon Chang Reak of Bang Saphan Noi. Security guards, their faces obscured by knitted balaclava headgear, are patrolling the road.
He said there was also someone trying to create the situation with gunshots and grenade attacks to former rubber farmers’ houses in the district on Thursday.
Pol Maj Gen Thanate said the police had to deploy more than 300 officers to collect evidence and there were several traffic cases to deal with as well. He said the road would be fully reopened only after the protests end.
The protesters' representatives and district chiefs had proposed taking responsibility for traffic control on the section of road that they had agreed to reopen, but police did not support the idea.
More than 3,000 rubber and oil palm farmers from various southern provinces have been campaigning for increases in the prices of their commodities.
They said the government had ignored their demands that the price of unsmoked rubber sheets be guaranteed at 100 baht a kilogramme and oil palm at six baht/kg.
On Monday, 10 companies of around 1,500 police were deployed to contain the rubber protest amid fears that the rallies may spread beyond Bang Saphan district.
Sommai Panthong, chairman of the Kamnan and Village Chiefs Club of Prachuap Khiri Khan, expressed his concerns about the ongoing protests, saying communities had become divided and arguments had arisen between protesters and local villagers.
He agreed that the protest should end through negotiation and the protesters should return Phetkasem Road to the public as soon as possible because a lot of damage had already been done.
The two-lane route used as a detour around part of the Phetkasem Highway in Prachuap Khiri Khan has been heavily damaged by the overwhelming number of vehicles, especially transport trucks, with repair costs already estimated at 30 million baht.