Prayut posted the photos of himself and his wife on his Facebook wall at 11.15 on Wednesday.
One of the photos shows the former prime minster smiling while touching his wife’s shoulder.
Another photo shows the couple walking in a Japanese park with Prayut wearing a cap, sunglasses and a brown jacket.
“Hello. This was the first time in more than 10 years that I’ve had a chance to take my family on a vacation abroad,” Prayut wrote in the post.
“I would like to show you photos from the trip. And I hope to have a chance to visit several more beautiful tourist sites both in Thailand and abroad.”
He said several Thais greeted him during his Japan trip.
By 2pm, his post had drawn more than 32,000 likes and been shared over 2,000 times.
After seizing power in a coup on May 20 2014, Prayut served two terms as PM, the first heading an interim government and the second following the 2019 election when he was nominated as the prime minister candidate of the Palang Pracharath Party.
While in office, Prayut devoted his time to running the country and often complained he had no time for a vacation with his family.
Prayut announced his retirement from politics after his United Thai Nation Party failed to win the election this year.