Thein Sein's ordination as a monk took place yesterday, officials said, four days after he presided over a historic transition of power to the former opposition party headed by Aung San Suu Kyi.
Photographs circulating on social media show the former president, with his head shaved and dressed in a saffron robe, beside a fellow monk.
The Ministry of Information released a statement on its Facebook page saying Thein Sein will spend five days in the monkhood.
A temporary stint at a monastery is common in the predominantly Buddhist country, where boys are expected to ordain as novice monks at some point in their childhood and then return later in adulthood.