Thai Air Force spokesman Air Vice Marshal Monthol Sutchukorn said the US authorities would be solely responsible for the comprehensive investigation to find the cause of the accident because the incident happened during the joint military exercise.
He said the Cobra Gold 2013 Operations Command and the US embassy in Thailand would provide all information to determine the facts and circumstances surrounding the incident.
AVM Monthol said the Royal Thai Air Force Safety Center provided staff to support the investigation by the US authorities.
A US military helicopter taking part in the Cobra Gold 2013 joint maneuvers made an emergency landing in Thailand's Phitsanulok province Wednesday.
Four of the seven US marines aboard the CH-46 Sea Knight helicopter were injured in the accident.
The US Marine Corps joined the US Army, US Navy and US Air Force in the 11-day multinational military exercise in Thailand which ends today.
An estimated 13,000 armed forces members from seven countries participated in the Cobra Gold exercise, including those from Singapore, Malaysia, Indonesia, Japan, South Korea, the United States and Thailand.