The Royal Thai Army has grounded its fleet of Bell 212 medium-twin helicopters after a fatal crash on 24 July in the west of the country that left three dead.
It is the latest in a series of helicopter crashes in Thailand during the past 10 days, with 17 fatalities.
According to local media reports the 212 was lost in benign conditions as it flew to participate in a search-and-rescue mission near the border with Myanmar.
The aircraft was heading toward a mountainous, heavily forested area northwest of Bangkok.
It was participating in an operation to retrieve nine bodies from the site of a Thai army Sikorsky UH-60 Black Hawk crash on 19 July.
The Black Hawk was lost while attempting to retrieve five bodies from the site where a Bell UH-1 helicopter crashed on 16 July.
The army believes weather played a part in the first two crashes, but not the third.
"Overall the Thai military buys lots of equipment, but not enough support in terms of spares and fuel to keep current," an industry executive familiar with regional helicopter operations said.
"In Thailand they were flying in challenging conditions in older equipment."
The executive added that fewer training resources meant helicopter pilots in some of Southeast Asia's air forces can be less proficient in instrument flying than their counterparts in the west. This can be a safety concern when coupled with low visibility and rough terrain.
On 17 June, the US Defense Security Cooperation Agency said Thailand had requested three Sikorsky UH-60M Black Hawk transport helicopters in a deal worth $235 million.
The possible purchase also includes eight General Electric T700-701D engines, including two spares, plus radios, identification friend-or-foe transponders and other related services and equipment, the agency said.
Earlier this year, Thailand took delivery of six Mil Mi-17 helicopters. In 2008, Thailand put its decision to purchase the Russian helicopters down to cost. The army said one Mi-17 costs one third of the price of a Black Hawk and can carry 30 troops, compared with the US helicopter's 13.
- According to Flightglobal's HeliCAS database, the Royal Thai Army operates 54 Bell 212s.