Police are to seek arrest warrants for six leaders of the Aug 10 political gathering at Thammasat University's Rangsit campus in Pathum Thani.
The six were identified as Panusaya Sithijirawattanakul, Panupong Chadnok, Arnon Nampa, Natchanon Phairot, Thanawat Chanphluek and Sitnon Songsiri, according to a police source.
They are now wanted in relation to offences allegedly committed at the rally, namely sedition, violations of the computer crime law, violations of the disease control law and advertising using loudspeakers in public areas without permission.
Parit "Penguin" Chiwarak, a student activist, reacted on Facebook on Tuesday to news that police would seek arrest warrants for the six protest leaders.
"My six friends who organised the Thammasat Cha Mai Thon (Thammasat will no longer put up with it) will face arrest warrants for sedition (Section 116 of the Criminal Code). Oh, for heaven's sake!" wrote Mr Parit.
He insisted rallying inside the university that day did not cause any disturbance and was peaceful.
Mr Arnon and Mr Panupong were arrested on Aug 8 for their roles in the July 18 anti-government protest at Democracy Monument, while Mr Parit was nabbed last Friday over his role in a rally in front of the Royal Thai Army headquarters on July 20.
The trio face several charges, including sedition, and were released on bail on the condition that they must not repeat the alleged offences.
Prime Minister Prayut Chan-o-cha said last week the authorities were looking to identify people who rallied for monarchy reforms at Thammasat on Aug 10.
Students have hit the streets in recent weeks, demanding the resignation of Gen Prayut's cabinet, the dissolution of parliament and the drafting of a new constitution. At the Aug 10 rally, students expanded their demands to include reform of the monarchy.
The move has apparently angered royalist groups, including the Coordination Centre for Vocational Students and People Protecting the Institution, aka Archeewa Chuay Chart (ACC), which has carried out counter-rallies warning their opponents to stop offending the monarchy, which is illegal.
The ACC, which mostly attracts older crowds, has held rallies at the same venues as the anti-government protesters but at different times. This raised concerns of a clash between the two groups, although so far no violence has occurred.