Ex-policeman Prathin Chankate, 60, (left) and civilian Natthapol Nawanle, 26, were both previously involved in the controversial "Khon Kaen model" arrests shortly after the 2014 coup. The military says the two had plans to bomb Bangkok, up-country sites and assassinate Prime Minister Prayut Chan-o-cha and Deputy Prime Minister Prawit Wongsuwon. (Photo by Pornprom Satrabhaya)

Prime Minister Prayut Chan-o-cha has accused the United Front for Democracy against Dictatorship (UDD) of being behind an alleged plot to instigate unrest and possibly attack key figures during festive events in Bangkok and the provinces.

According to the government, those targeted for attack by the group include Gen Prayut and Deputy Prime Minister and Defence Minister Prawit Wongsuwon.

In response, the UDD said the government is "inventing a story" in order to deflect attention from the scandal surrounding the Rajabhakti Park project.

Soldiers on Thursday handed over a former police officer and a civilian arrested in Khon Kaen for allegedly conspiring to instigate unrest in Bangkok to police for questioning.

They are Pol Sgt Maj Prathin Chankate, a 60-year-old former border patrol policeman, and Natthapol Nawanle, 26.

The suspects face charges of breaching Section 112 of the Criminal Code, known as the lese majeste law, and violating the Computer Act after authorities found them "hatching a plot to stir unrest in the city" and contacting each other to discuss attack plans via the Line application, national police chief Pol Gen Chakthip Chaijinda had said previously.

The arrests came after authorities discovered a group of people in the Northeast were planning to cause chaos in Bangkok during the Loy Krathong festival, the King's birthday, the "Bike for Dad" event and during New Year celebrations, security sources said.

Pol Gen Chakthip said the group was found to have planned an attack involving important figures.

When asked if any political groups were behind the alleged plot, Gen Prayut said Thursday the suspects arrested were members of the UDD.

"Which group do they belong to? They call themselves the UDD, don't they?" Gen Prayut said, adding that the alleged plot was tied to the so-called "Khon Kaen model" armed network believed to have been linked to the red-shirt movement.

The prime minister also denied that the government fabricated the story involving the alleged plot in order to shift public attention from the Rajabhakti scandal.

Gen Prayut said the alleged plot against key figures would not deter him from visiting the provinces, particularly the Northeast which is a stronghold of the red shirts.

"I can visit any province. Today, I already risked my life. But I am not afraid," the prime minister said.

Gen Prawit also insisted authorities had solid evidence relating to the alleged plot to attack government figures including himself and the prime minister.

However, UDD chairman Jatuporn Prompan said the UDD has maintained a peaceful approach and had no plans to act against the government.

The military was closely shadowing all UDD key figures to restrict their actions, so there was nothing they could have done to challenge the government, Mr Jatuporn said. He echoed the UUD's claim that the alleged plot was a fabrication.

"There is no need for anyone to do anything. The government is already collapsing. Nothing can cover up for the Rajabhakti corruption," he said.

Pol Maj Gen Chayapol Chatchaidej, commander of the Counter Crime Planning Division, said apart from the two suspects, there were seven other people suspected of being involved in the alleged plot to stage unrest.

The Bangkok Military Court has also approved arrest warrants for them, Pol Maj Gen Chayapol said.

The seven others in the team who are still at large are Phitsanu Promsorn, 58, Wallop Boonchan, 33, Chatchai Sriwongsa, 24, Meechai Muangmontree, 49, Thanakrit Thongngernperm, 49, Veerachai Chaboonmee, 33, and Pahiran Kongkham, 44.

Pol Maj Gen Chayapol said that Pol Sgt Maj Prathin and Mr Natthapol were among the defendants facing terrorism charges for their alleged ties to the so-called Khon Kaen model.

The two suspects had been out on bail before they were arrested again.