Police have apprehended another man in the group of nine suspects wanted under warrants for lese majeste and computer crimes, bringing the total number of arrests in the case to five, reports said.
The nine have been linked to the so-called "Khon Kaen Model" group, whose members were earlier arrested in a sedition case.
Of the nine suspects, four had been arrested earlier - Pol Sgt Maj Prathin Chanket, 60, Nathapol Na Wanle, 26, Wallop Boonchan, 33, and Pahiran Kongkham, 44.
Police identified the fifth man arrested as Chatchai Sriwongsa, 24, but did not say when he was caught or where. He has been handed over to the Crime Suppression Division, which will seek approval from the military court to detain him for the first 12-day period for interrogation.
Another suspect - Thanakrit Thongngernperm, 49 - is still incarcerated in Khon Kaen prison in another case.
The three suspects still at large are: Pitsanu Promsorn, 58, Meechai Muangmontri, 49, and Veerachai Chaboonmee, 33.
The warrant for the arrest of Thanakrit prompted his lawyer, Benjarat Meethien, to file a countersuit with Crime Suppression Division police, naming Maj Gen Wijarn Jodtaeng, the legal chief of the National Council for Peace and Order, Pol Gen Srivara Rangsibrahmanakul, a deputy police chief in charge of investigation of lese majeste cases, and their staff.
It accuses them of abuse of authority, defamation and laying a false complaint against Thanakrit.
Ms Benjarat said her client had been imprisoned at Khon Kaen prision since May last year and could not have been complicit in the alleged offences.
In response to questions on Monday, Deputy Prime Minister Prawit Wongsuwon said the warrant issued for Thanakrit's arrest was properly approved by the court.
Ms Benjarat said considering the tight security at Khon Kaen prison it was not possible for her client to have committed such offences while an inmate there.
Gen Prawit said that although Thanakrit was in prison he must have done something against the law, otherwise the court would not have approved the warrant for his arrest.