The plane was conducting a test flight to prepare for parachute training in Hua Hin district before it crashed around 8 am, said Royal Thai Police spokesperson Archayon Kraithong.
Officials did not immediately share the model of the propeller plane, but photos from the scene appear to show a Viking DHC-6 Twin Otter. The plane crashed near Hua Hin Airport, said the public relations department of Prachuab Kiri Khan province.
The photos show the plane in the sea about 100 meters off shore. The body of the plane appeared to be broken in two.
All six people on board were police officers, Archayon said, adding that five died at the scene and one died later at a hospital.
The cause of the crash was not immediately known. Archayon said officials are gathering evidence including data from the plane’s black box.
