When he was appointed army chief in 2010 he was seen as something of a hardline royalist, opposed to the Red Shirt movement that has largely backed the Governments of Thaksin Shinawatra and his sister, Yingluck.
Yet after he took charge he appeared to reach out to the Red Shirts and made an effort to get along with Yingluck.
"He participated in the 2006 coup, led the repression of Red Shirts in 2010 and advocated even tougher action against the Red Shirts from 2009-2011. Under Yingluck, he appeared to be neutral," said Dr Paul Chambers, of the Institute of Southeast Asian Affairs at Chiang Mai University. "But as it turns out now, he was playing a game with the Shinawatras. On May 20, with the application of martial law, he has shown his true arch-royalist colours."
Prayuth has had a notoriously difficult relationship with the media, often snapping at reporters and chastising them for asking "stupid" questions. Just this week, he advised one reporter to "go to the ear doctor" after asking about whether or not elections could proceed.
Prayuth is part of the army's most powerful faction, known as the Eastern Tigers. His term in office was due to end in September but there is speculation now that if he does stand down as acting prime minister, he could be allowed to stay on as army chief for another year.
In May 2011, a prominent opposition MP and Red Shirt leader, Jatuporn Promphan, was imprisoned after being charged with making comments deemed to be disrespectful of the monarchy -- a very serious offence in Thailand and one which carries with it the risk of 15 years in jail.
The BBC reported that the case against Jatuporn, one of the Red Shirt leaders detained yesterday, was prompted by a complaint from Prayuth.
He insisted at the time that his motive was not political but rather to protect the monarchy.
Further questions were asked about him in the summer of 2011 when Thailand was holding an election. The general said that he believed people should vote for "good people", a comment that was widely seen as an attack on Yingluck. As it was, she went on to win.
- Independent