An embassy spokesman, speaking in Bangkok, said no one was killed in the incident involving a CH-46 Sea Knight helicopter carrying U.S. personnel participating in the Cobra Gold joint military drills, The Bangkok Post reported.
A source told the Post two helicopter passengers may require surgery. Another passenger sustained minor injuries and three were not hurt.
The reason for the hard landing wasn't reported.
Cobra Gold is a joint field training exercise involving troops from the United States, Thailand and other countries.