Krabi marine police nabbed Alongkorn Chonlathee, 30, and Prakai Uiwong, 26, for fishing illegally off the coast of Phi Phi Island.
Pol Major Thaweelap Suwannareuk, a Krabi marine police inspector, said Alongkorn was driving the speedboat, while Prakai was doing the killing.
The two have pleaded guilty and admitted to doing what the clip shows, Thaweelap said.
Alongkorn faces a 10,000 baht for using a speedboat without permission, while Prakai will be further investigated before a penalty is decided for him.