Kuo Yu-chen, 55, was quickly overcome by the gas when he went to check on the cooling system in the hold of the tuna long-liner Shun Ying 668, at about 7:50am, before the boat departed for its daily catch, one crewman told The Phuket News.
“Mr Chen shouted for help, so other crewmen went below to help him,” he said.
The fellow crewmen shut down the cooling system, but were unable to bring Mr Chen, who was now unconscious, back up through the hatch to the upper deck.
Kusoldharm Foundation rescue workers soon arrived and pumped the gas out of the lower deck before recovering the unconscious Mr Chen.
He is now at recovering at Phuket Provincial Hospital and has regained consciousness, The Phuket News was told.
Phuket Marine Police Chief Lt Col Panya Chaichana has ordered his officers to investigate the incident and find out what caused the leak.