The attack left 54-year-old Thaweesak – chief of Tambon Por and president of the Hmong People Club of Thailand – and his three-year-old son seriously injured. His wife and five-year-old daughter were killed.
Police suspect that Thaweesak’s role in the recent arrests of drug suspects might have prompted the attack.
Chiang Rai police chief Pol Maj General Yutthachai Puaprasert led Wiang Kaen precinct police officers in the pre-dawn raid in Ban Huai Han (Moo 9).
Soldiers from the Northern Border Drug Prevention and Suppression Operations Centre, paramilitary rangers and Border Patrol police also participated.
The search turned up no illegal items.
Officers led by Provincial Police Region 5 deputy chief Pol Maj General Churat Pan-ngao and Wiang Kaen administrative officials had the day before seized about 300 legally registered guns for inspection.
Police are hoping to find weapons that match spent cartridges recovered at the scene of the ambush.