The Muang Prachin Buri police station was alerted of the suicide at 12.30am.
The body of Pol Sr Sgt-Major Patiphat Prempran, 55, a former border patrol policeman, was found lying in front of a closet on the ground floor of the two-storey townhouse. He had a gunshot wound to his left temple and his 9mm pistol was found nearby.
His wife, Angkhana Prempran, 63, told police she was watching TV when she heard a gun fire and found her husband already dead.
Angkhana said Patiphat took an early retirement in 2013 and worked as a driver for a local politician. She said he used to complain about his Bt800,000 debt with a police savings cooperative and said he would like to die because of the debt.