A student activist was snatched from a Bangkok street, bundled into a car and assaulted by soldiers, his lawyer said on Thursday, in a dramatic act of military muscle-flexing apparently caught on CCTV. The activist, Sirawitch Sereethiwat, has been a perennial thorn in the military's side since it seized power in 2014 and clamped down on freedom of expression and public dissent in the kingdom. Widely circulated security camera footage appears to show three uniformed soldiers grab Sirawitch on a busy street outside his university late Wednesday night. The 24-year-old student is then 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 Thursday at a Bangkok police station with violating a junta ban on protests and political gatherings, Pawinee Chumsri, of Thai Lawyers for Human Rights, told AFP. In a video clip filmed Thursday at the police station, Sirawitch, also known as Ja New, said he was blindfolded, slapped and kicked while in military custody. "He was abducted and physically assaulted," Pawinee said, repeating the allegations. "This is an enforced disappearance and arbitrary detention. It's illegal." Three other activists -- all members of the student-led 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 for campaigning against a controversial multi-million-dollar park built by the military that has been dogged by graft allegations. Mass protests were staged outside of Bangkok's Thammasat University -- where Sirawitch and other New Democracy Movement members are students. 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 since the May 2014 coup. 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 authorities. In typically flippant fashion, Thailand's stern junta leader brushed off the students' arrests and took a swipe at Siriwitch's academic status. "I want to ask how long he has been a student and when he will graduate," Prayut Chan-O-Cha told reporters. 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. 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.