The UH-1 helicopter disappeared while carrying telecommunications equipment and food to a radar base located in the Khao Chamao-Khao Wong National Park in Chanthaburi province.
Two helicopters from the air force and navy personnel are involved in the search operation that was canceled at nightfall after three hours of tracking.
The Thai armed forces have suffered several helicopter accidents in recent years due to technical malfunctions and visibility issues.
In 2011, 17 soldiers died in three helicopter crashes in the mountainous region in western Thailand while in 2014, nine soldiers were killed in an accident involving another unit in the north of the country.
- EPA