Prime Minister Prayut Chan-o-cha has accused fugitive former prime minister Thaksin Shinawatra of being behind the recent resurgence in opposition to his military regime.
Thaksin's key supporter immediately denied the claim.
Gen Prayut named Thaksin as reporters repeatedly sought his comments on Thursday about demonstrations against his government and the detention of his critics, and on the people behind such activity.
"Do you really not know about the questions you ask? I seriously wonder if you really have no idea... Who is doing this? Who supports it? Who plans? Foreign lobbyists. It is Thaksin," Gen Prayut said.
Asked about student demonstrations, the prime minister loudly responded, "Which side are the students on? Who provided the vehicle transporting them? Did Voice TV take them? Did a UDD vehicle take them?"
Voice TV is run by Thaksin's children. The UDD is the United Front for Democracy against Dictatorship, the pro-Thaksin political group also known as red-shirts.
Gen Prayut assured reporters that demonstrators who broke the law would be prosecuted and tried in court.
Responding to further questions about international concern about people's liberty and the detention of Pheu Thai Party figure Watana Muangsook, Gen Prayut said he would write to them, and to all ambassadors and explain the record of law violations by demonstrators and by people who had fled prosecution. These records included corruption cases, he said.
Thaksin has been in self-imposed exile since 2008. He fled the country just before the Supreme Court sentenced him to two years in prison for abuse of authority.
Gen Prayut said he had been kind on several occasions and it was time to seriously enforce the law. He urged people to think carefully about who was really behind the disorder, and if the demonstrators were sincerely motivated.
Gen Prayut also said demonstrations could block the charter referendum, just as past protests had obstructed elections.
Thaksin supporter and former foreign minister Noppadon Pattama said on Thursday that the former prime minister had not hired any lobbyist in another country to help organise protest activity.
Thaksin was a person of little consequence overseas and could not influence any international organisation or any governments that normally receive reports on the situation in Thailand, he said.