Chalong Police, under the command of Col Sarawut Chuprasit, together arrested the suspects at about 1:30pm.
The 20 men were found with 10 fighting fish in five jars and 14 kratom leaves. Officers also seized B8,550 in cash and a notebook which was used to record the results of the fish fights.
The men were taken to Chalong Police Station and charged with illegally gathering under the emergency decree, illegal gambling and possession of a Category 5 drug.
Phuket Provincial Police publicly posted that the arrest came after their commander, Maj Gen Pornsak Nuannoo, reminded officers at every police station on the island to frequently patrol areas under responsibility.
Officers also asked for cooperation from local residents to strictly follow the disease control measures enacted into force by the Phuket provincial government.