Phuket police said the five burmese workers were found in a single-story office at a construction site in front of Baan Kuku market on Ratsadanusorn Rd, Phuket Town, passed out from carbon monoxide poisoning from an electrical generator running in their room.
The workers' foreman was unable to wake the men on Sunday morning (November 4), and called police and the hospital at around 10am.
The 30 year old was already dead. The four other injured men were taken to Vachira Hospital, where one later died.
Sataporn Pitakkul, the site foreman, said the men worked for the Siwapat company. Saturday night was the first night they spent at the location. Mr Sataporn suspected the workers might be drunk and left the generator on with the doors and windows closed, meaning the gas was trapped in the room.
The men went to sleep at 8pm, and used the electrical generator because the office did not have electricity.
"The men inhaled too much carbon monoxide, starving the brain of oxygen which resulted in two of them dying,” said Doctor Weerawit Sariddipan, medical department chief from Vachira Hospital.
Police will investigate further.