The Bell 212 helicopter was supporting operations to retrieve the seven missing bodies from a Black Hawk crash on Tuesday when it went down and caught fire in western Phetchaburi province.
Two bodies were found on Saturday, including that of a television cameraman.
Tuesday’s fatal mission was to retrieve the bodies of five army personnel who died when another Vietnam War-era helicopter went down in bad weather last weekend.
Army spokesman Sansern Kaewkamnerd said the sole survivor of Sunday’s crash, a mechanic, reported a problem with the helicopter tail and the cause was likely to be engine trouble.
Channel 3 television showed a mangled helicopter in flames in a rugged patch of land. Witnesses said they spotted a problem with the tail of the aircraft before it went down.
The first two helicopters that crashed had flown over hilly jungle terrain in a rain-soaked region. Air missions have been conducted daily because rescue teams were unable to scour the area on foot.
Military helicopter accidents have occurred with startling frequency in Thailand, with three Bell UH-1H choppers crashing between June and October 2008, due to engine trouble or bad weather.
Most of Thailand’s military helicopters were procured from the United States and many were used during the Vietnam War.
Army commander-in-chief Prayuth Chan-ocha told local television the missions to retrieve the missing bodies would continue and latest crash would not deter the army from using its helicopters.
