The two were arrested last month on charges of sedition and breaching the emergency decree and public health rules, among other alleged offences.
Arnon had been granted bail on August 8 after being arrested for attending an anti-government gathering on July 18.
Police arrested him again on August 19 after his participation in an August 3 rally speech at Bangkok’s Democracy Monument.
Police issued a third arrest warrant against Arnon after he attended an August 10 protest at Thammasat University’s Rangsit campus. Phanuphong was first arrested on August 7 and again on August 24. The Bangkok Criminal Court revoked bails for both of them due to alleged repeated offences.
The protest in front of the prison was a peaceful one with speeches by anti-government activists interspersed with music performance on stage. At 10pm the protesters light candles in front of prison gate while singing together before dispersing.