The Central Administrative Court has dismissed the case in which former minister Wattana Muangsuk asked it to revoke the junta's order banning 155 people from going abroad.
Court vice-president Sopon Boonkul rejected and dismissed the case on Monday.
The National Council for Peace and Order (NCPO) order No. 21/2557 prohibits 155 people, mostly politicians, from leaving the country without the junta's prior permission.
Mr Wattana had asked the NCPO for permission to go to Singapore on July 17 but the junta had rejected his request, saying he had been allowed to leave the country six times already.
Mr Wattana therefore turned to the court to give him an injunction from the order, which he claimed was illegitimate.
- Earlier report: Wattana sues Prayut over travel ban
The court on Monday cited Section 47 of the 2014 interim charter, which provides all NCPO orders and acts are "legal, constitutional and conclusive".
A source said Mr Wattana and his group wanted to go abroad to celebrate former PM Thaksin Shinawatra's 66th birthday on July 26.
After learning the court's decision, Narinpong Junpapak, his lawyer, said he would discuss it with Mr Wattana.
"We will appeal the decision as we think the order violates laws and the liberties the NCPO itself endorses," he told Thai media.