Search and rescue teams found the missing helicopter at a deep valley adjoining Chanthaburi and Rayong provinces with all three crew members killed at the crash scene.
The search team reached the crash scene on foot at 10.23am.
The team was calling in helicopter to lift the three victims and sent them back to their base at Don Mueang Air Force base in Bangkok late today.
The crew members included a pilot, a co pilot and a mechanic.
They were flying a Huey helicopter from Don Mueang base to deliver supply to a radar station on a mountain top in Chanthaburi last Saturday.