Army chief Gen Narongphan Jitkaewtae left for Hawaii on Sunday night and will return late this month.
Gen Narongphan flew out to attend the Land Forces of the Pacific (LANPAC) Conference in Hawaii from Monday to Thursday. He would then visit the US Army Pacific (USARPAC) headquarters in Hawaii, the announcement said.
He was scheduled to return to Thailand on May 28, a source said.
The army chief's trip is at the invitation of Gen Charles Flynn, commanding general of USARPAC, who visited Thailand last month.
His departure came as the Move Forward Party took the lead in Sunday's general election and planned to form the next government. The party earlier announced a policy to reform the military.
Last week the army chief said that if the Move Forward Party was able to form the next government, or if there is policital unrest after the general election, the military would not stage a coup.