Authorities stated that nine passengers on a charter jet that crashed the day before were believed to have died, and Thai rescuers searched the muddy, forested area with hoes on Friday in an attempt to find any remains.
About 100 kilometers (62 miles) southeast of Bangkok, a Cessna Caravan C208B aircraft, carrying five Chinese tourists and four Thai nationals, including the two pilots, went down 11 minutes after takeoff after they lost contact with ground control.
As authorities rushed to determine the reason for the incident, Chonlatee Yongtrong, the governor of the province of Chachoengsao, where the charter plane crashed, declared that all occupants were presumed dead.
The governor told reporters late on Thursday, "We found many human remains," noting that the swampy terrain made the search more difficult.
"The plane dropped vertically, so we have to dig 10 m (33 ft) into the ground."
Images from the site reveal a forested, marshy area covered in scattered aeroplane debris. Rescue personnel are using hoes to excavate and a pump to remove water from certain spots, while police forensic teams are working to recover and reconstruct the bodies.
On Thursday afternoon, the aircraft, operating flight TFT209, departed from the capital's Suvarnabhumi airport and made its way to the eastern province of Trat.
According to the aviation regulator, the aircraft was registered to Thai Flying Service Co Ltd., and 11 minutes after takeoff, provincial officials said, the plane lost touch with ground control in Bangkok.