Assistant army chief Thirachai Nakwanich has been confirmed as the new head of the army in a military reshuffle list endorsed by His Majesty the King.
Gen Thirachai will succeed Gen Udomdej Sitabutr, who will retire at the end of September, according to the list, which was published in the Royal Gazette on Friday night after receiving the King's endorsement.
Preecha Chan-o-cha, another assistant army commander, will become the permanent secretary of the Defence Ministry.
The younger brother of Prime Minister Prayut Chan-o-cha had been tipped as a contender to head the army, reportedly with backing from Gen Udomdej, although he was in the same class as Gen Thirachai at the Armed Forces Academies Preparatory School.
Gen Thirachai was believed to be the choice of Defence Minister Gen Prawit Wongsuwon, as his career included service in the Burapha Phayak, or Tigers of the East, at the 2nd Infantry Division in Prachin Buri province.
The army leader-in-waiting commanded the 1st Army in charge of Bangkok and central provinces before being promoted to his present post. The group played a key role in the coup last year led by Gen Prayut, then the army chief.
Gen Preecha came to army headquarters after serving as commander of the 3rd Army, with responsibility for security in the northern region.
The new navy commander will be Adm Na Areenij, currently chief-of-staff. He edged out assistant navy chief Adm Narongpol Na Bangchang.
Adm Na emerged as the frontrunner at the last minute after the defence minister reportedly made it known that he wanted to keep the tradition of reserving the top navy job only for graduates of the Naval Academy. Adm Narongpol, who is an expert on submarines, studied at the German naval institution.