Almost 1,000 police and soldiers are expected to be deployed to step up security at Government House, which hosts a public forum Friday on the controversial oil and gas exploration concession bid.
About 750 police from the Metropolitan Police Bureau (MPB) will be on hand while the army will send 200 troops to boost security, a source said.
At least seven civic groups who are opposed to the 21st round of bidding have expressed an interest in joining the forum.
The government's complaint centre at the Office of the Civil Service Commission, opposite Government House, is being prepared for those who are interested in the forum but have not been invited to attend.
The source said Prime Minister Prayut Chan-o-cha has ordered the MPB and Col Khachachart Boondee, commander of the 1st Artillery Regiment, to take charge of security operations.
The security forces have also been told to screen people entering Government House.
The forum was called by the government following growing opposition to the 21st round of concession bidding.
The Energy Ministry delayed the process for a month after the government came under pressure to review the bidding process.
Gen Prayut said Thursday he expects a mutual conclusion to be reached following the forum. He was asked if he has a back-up plan if the two sides could not iron out their differences.
The prime minister suggested the media seek the views of those who do not turn up for the forum, as they deserved to be considered, too.
"The whole country should be asked what they think about this. We have these civic groups and the state authorities. What about the others who haven't voiced their opinions? The media should ask them what they think after the forum," he said.
Gen Prayut said the government would consider alternatives to the concessions if the Energy Ministry could not argue against the reasons presented by the scheme's opponents.