Local authorities were informed of the incident at about 5pm yesterday (Apr 24).
The ambush happened late yesterday afternoon on the Ban Rom Fa Thong-Ban Pha Tang Rd in Ban Rom Fa Thong village in tambon Por of Wiang Kaen district.
Police responding to the emergency found a silver Toyota pickup truck registered in Chiang Rai with licence plate number Phor Khor 4115. There were numerous bullet holes through the windscreen, both sides and the rear of the pickup.
The driver was identified as Thaweesak Yodmaneebanphot, 54, kamnan of tambon Por and chairman of the Hmong Club in Thailand.
His passengers were his wife Maiyia Wongnapapaisal, 40, their five-year-old daughter Thanyaporn Yodmaneebanphot and their three-year-old son Chaimongkol Yodmaneebanphot.
The wife and daughter were both killed at the scene. Mr Thaweesak and his son, severely wounded, were taken to a local hospital.
The ambush took place on a curve of the road that passes through a forested mountainous terrain.
Police believe the family were on their way home.
No motive for the attack has been determined, but police said they were investigating a possible business conflict.
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