Student activist Sirawith "Ja New" Seritiwat has been released on bail and is required to report to the Thon Buri railway police station early Monday, police said.
Mr Sirawith, a Thammasat University student and leader of the New Democracy Movement, was arrested on Saturday at the annual Chulalongkorn-Thammasat football match under a Military Court warrant issued on Thursday for failing to answer a summons to report to police.
He is one of several people who have been charged with illegal assembly for an attempted protest last year over alleged corruption in the construction of Hua Hin's Rajabhakti Park.
Undercover police arrested him at the National Stadium on Saturday and placed him in a taxi which took him to the Thon Buri railway police station.
Pol Lt Col Phakphum Decharuangsilp, an investigator at the police station, revealed on Sunday morning that Mr Sirawith was released at about 11.30pm on Saturday after a woman, Aida Arungwonse Na Ayutthaya, 42, applied for his temporary release with a 10,000 baht surety.
The bail guarantor was required to bring Mr Sirawith to the Thon Buri railway station on Monday at 8.30am. After that he would be handed over to Military Court prosecutors for further indictment.