BANGKOK (AFP) - A student activist was snatched from a Bangkok street, bundled into a car and assaulted by soldiers, his lawyer said on Thursday (Jan 21), in a dramatic act of military muscle-flexing apparently caught on CCTV.

Widely circulated security camera footage appears to show three uniformed soldiers grab Mr Sirawitch Sereethiwat on a busy street outside his university on Wednesday evening.

The student, who has been a perennial thorn in the military's side since it seized power in 2014, is seen frog-marched into a white car and driven away in front of stunned bystanders.

He spent the night in military custody and was charged on Thursday at a Bangkok police station with violating a junta ban on protests and political gatherings, Mr Pawinee Chumsri, of Thai Lawyers for Human Rights, told AFP.

In a video clip filmed on Thursday at the police station, Mr Sirawitch, also known as Ja New, said he was blindfolded, slapped and kicked while in military custody.

"He was abducted and physically assaulted," Mr Pawinee said, repeating the allegations.

"This is an enforced disappearance and arbitrary detention. It's illegal."

Three other students - all members of the New Democracy Movement - were also arrested when they visited the police station and face action in a military court.

The four have been charged with violating the junta's ban on public gatherings by organising a trip to a controversial multi-million dollar park built by the military that has been dogged by corruption allegations.

The group has embarrassed the military with protests and brazen social media campaigns in defiance of the junta ban.

Outside of their activities there have been relatively few high-profile anti-coup protests across Thailand with the military tightening its chokehold on the country.

A junta spokesperson confirmed the arrest but denied the allegations of assault.

"He was treated leniently and in accordance with the law, there was no violence," Colonel Winthai Suvaree told reporters, adding that the activists have "refused to cooperate" with the authorities.

Col Winthai accused Mr Siriwitch of trying to "provoke the authorities", adding: "I don't know the real reason for this."

People who oppose the junta are routinely accused of being in the pocket of self-exiled former premier Thaksin Shinawatra, a billionaire who sits at the heart of Thailand's political rupture.

Thaksin and his parties have won every Thai election since 2001, facing two coups and the removal by the royalist courts of three premiers in that time.

His sister Yingluck was booted from office by a court ruling days before the May 2014 coup.

The military says it had to intervene to restore peace and order after mass protests against Yingluck's government.

Analysts say the military wants to be in control of the country during the twilight years of the reign of King Bhumibol Adulyadej, who is 88 and in poor health.