Prime Minister Prayut Chan-o-cha has warned political protesters not to disrespect the monarchy during their rally on Wednesday, which also coincides with a royal merit-making ceremony.
"We have been trying to ensure the safety of both sides and avoid confrontation. If they [protesters] do not disrespect the monarchy or slander anyone, no problem," he said.
"But what are they doing now? Can we allow what they have proposed, that they hate and disrespect the monarchy? Should everybody allow? [If so], I don't think Thailand can survive," he said referring to the protesters' plan to occupy part of the route which the royal motorcade will follow to reach the ceremony.
He said there will be tight security for the royal motorcade and a lot of people would be out to greet Their Majesties the King and Queen as they make their way to the royal kathin (monk robe-giving) ceremony, held annually following the end of Buddhist Lent.
Arnon Nampa, co-leader of the United Front of Thammasat and Demonstration (UFTD) and the Free People group, accused the police on Facebook of intentionally trying to disrupt the demonstration by having the royal motorcade pass by the rally site.
He said the police intend to set the scene to clash with protesters.
"If chaos breaks out, the police will be to blame, not the protesters," he wrote.
Mr Arnon, however, affirmed that protesters will not obstruct the royal motorcade as it heads to Wat Phra Sri Rattana Satsadaram (Wat Phra Kaeo).
This was announced in the media to be taking place at 5pm, around the time the protesters will gather on Ratchadamnoen Klang Avenue.
Pol Gen Damrongsak Kittipraphat, deputy national police chief, said police would try negotiating with the protesters first to try and ensure maximum security for the royal motorcade.