A team of police, accompanied by a doctor and volunteers from a charity foundation, went to house No 260 in tambon Chiang Wang at about 6:30am after being notified of the tragic incident.
They found the body of Thaisan Sonchai, 50, hanged with a green nylon rope to a branch of a mango tree in front of the two-storey house.
The bodies of his wife Watcharaporn, 50, and their two daughters Kachaporn, 23, and Sasithorn, 19, were found lying dead in the hall on the ground floor of the house. A 50-centimetre-long wooden stick was founded near the bodies. The three had been struck on the head with the wooden stick, leaving deep cuts on each. They were believed to have died six hours previously.
A note, handwritten by Thaisan on a sheet from a calendar, was found in front of the toilet.
In the note, Thaisan said he was badly indebted and unable to provide adequate financial support for his two daughters. He also offered an apology to all concerned for the trouble he had caused.
A tray of flowers, candles and incense sticks was placed by the bodies of his wife and daughters, probably by Thaisan, asking them to forgive him.
It was believed Thaisan killed his wife and daughters before taking his own life.
Boonchan Saenhemthong, 76, Thaisan's father-in-law, said Thaisan and Watcharaporn worked at the Zone 4 Sericulture Research Centre in Phen district. Their elder daughter, Kachaporn, was a graduate in food technology from Khon Kaen University but was still jobless, while the younger daughter, Sasithorn, was a first-year student at Khon Kaen University.
Mr Boonchan said Thaisan had obtained loans from financial institutions, amounting to about 2 million baht in total, to finance his daughters' education.