Officers from Kuraburi Police Station were called to a house in Moo 11, Khura subdistrict, at about 10am after reports of multiple people unconscious in a well behind the property.
At the scene, police and rescue workers found the bodies of four men inside the well. They were later identified as Suton Kongkaew, 41; Suthat Adam, 35; Theeradol Chueasongsa, 30; and Wahab Chueasongsa, 59.
According to witness testimony given to police, Suton had been digging the well behind the house when he suddenly lost consciousness. Suthat then climbed down to help him, but also collapsed shortly afterwards.
A relative, identified as Kusuma Adam, raised the alarm, prompting two more men, Theeradol and Wahab, to attempt rescues in turn. Both also lost consciousness after entering the well. None of the four were able to escape.
Rescue teams and local officials were alerted, but all four men were pronounced dead at the scene.
Initial investigations indicate the deaths were caused by asphyxiation, likely due to a lack of oxygen or the presence of toxic gases in the confined space. Police said the exact cause will be confirmed following a full post-mortem examination.
The bodies were recovered with the assistance of rescue teams and taken for forensic examination at Kuraburi Chaiyapat Hospital.
The incident was reported to Phang Nga Provincial Police, with Pol Lt Sarawut Phumisurarat leading the investigation.
Separately, Phang Nga Governor Pairat Petchyuan ordered the Provincial Disaster Prevention and Mitigation Office to coordinate the emergency response, with multiple rescue units deployed to assist in the recovery operation.
Officials have warned the public to exercise extreme caution when working in confined or poorly ventilated spaces, where oxygen levels can drop rapidly and toxic gases may accumulate unnoticed.