The carcass of an adult male gaur was found deep in the forest on Sunday about 120 metres from Prak Hang creek in Moo 6, tambon Khao Chao, Pranburi district. It weighed about a tonne and was believed to have been dead for about a week.
Prachuap Khiri Khan provincial police chief Pol Maj Gen Thanes Soonthornsook said a team of forensic and police officers led by Pranburi police station chief Pol Col Wanchai Tharanatham inspected the area where the carcass had been found on Monday morning.
The team walked three hours before reaching the spot.
They discovered two spent shotgun cartridges nearby, indicating the animal had been shot before having its head cut off. The killers had butchered about 800kg of flesh and burned the animal's body to cover their tracks, Pol Maj Gen Thanes said.
It is believed the perpetrators killed the gaur to sell its head and horns on the black market for around 50,000-80,000 baht, while its flesh was likely to be sold to restaurants serving wild animal meat, he said, adding that police were checking on restaurants from Hua Hin to Muang district.
The team was able to detect fingerprints at the scene and collected blood samples from the gaur as evidence.
Pol Maj Gen Thanes confirmed the gaur did not die of natural causes. It's death was not related to the deaths of 24 rare gaurs in the park late last year, which latest laboratory tests indicate were caused by foot-and-mouth disease.
Investigators are assuming the suspects are based in the vicinity of the park, but are yet to conclude whether the killing was the work of Thai or Karen hunters living near the border.