The incident, which took place in May, has shocked locals and animal rights group Watchdog Thailand has been pushing for justice.
Chang Phueak police station reportedly has evidence of the animal being taken out of the campus at night, tortured and the body being dumped by the suspects.
Apart from the dismissal of one suspect, a committee will also be set up to investigate the case.
National police chief General Chakthip Chaijinda himself has said he will ensure justice is served.