He was arrested from Mongsangei Makha Leikai Arubam Leikai near Puthiba Laibung Complex on Sunday, it said.
To date, 10 people, including seven AT members, have been arrested in connection with the murder, the statement said.
Chesam went missing on the midnight of June 11 and his body was later found buried at Samurou Naorem in Imphal West district.
The body was exhumed on June 17 in the presence of an executive magistrate, forensic team and family members.
A criminal case was registered and a thorough investigation was being conducted, police had said.
The killing sparked protests and condemnations by multiple Muslim bodies in Imphal Valley. PTI CORR ACD