Thailand's junta leader has officially become the new prime minister following a royal endorsement from the country's monarch.

During a ceremony in Bangkok, Gen. Prayuth Chan-ocha accepted a written royal command issued by King Bhumibol Adulyadej certifying his appointment as Thailand's 29th premier.

Bhumibol, who is 86 and in ill health, was not present at Monday's ceremony.

Thailand's junta-appointed legislature voted overwhelmingly last week to name the 60-year-old army chief to the new post. He was the only candidate.

Prayuth overthrew an elected civilian government in a May 22 coup, and analysts say his new post cements the military's control of the country.

Prayuth is due to retire from the military next month and will hold both posts until then.