The plane crashed at around 3 pm (local time) in Khok Samrong district of central Lopburi province.
"The pilot could not eject himself out of the plane in time," Lopburi governor Thanakom Chongchira told AFP by telephone.
The cause of the crash, which took place near an airforce training centre, is under investigation.
In November nine soldiers on board an army helicopter died when the chopper crashed in northern Thailand.
In July 2011 a series of helicopter crashes in the space of a week forced the Thai army to ground much of its fleet.