Gen Prayuth, in an address to senior military officials, announced the date as part of a three-phase plan of reconciliation, formation of a government and elections to be rolled out by the coup-makers' National Council for Peace and Order (NCPO).
"A government will be set up by August, or at the very latest September," Gen Prayuth told a meeting devoted to the 2015 national budget.
Gen Prayuth repeated in his address that a temporary constitution would be drafted within three months. It would take at least a year until a new general election could be held.
"In the next three months we must do everything properly, whether it is the constitution or other matters. Everything for the first phase should be complete by August," Gen Prayuth said.