Most of those powers had not been invoked this week, but the military has taken steps to muzzle the media.
Prayut gave no indication how long the military would hold power but said it took over in order to “start political reform.”
Prime minister Yingluck Shinawatra was dismissed from office earlier this month in a controversial court ruling that left her caretaker successor clinging to power.
Nearly seven months of streets protests have left at least 28 people dead and hundreds wounded.
The crisis broadly pits a Bangkok-based royalist elite and its backers against the billionaire family of populist former premier Thaksin Shinawatra – Yingluck’s elder brother.
Thaksin was ousted by the military in 2006 and now lives in exile but still enjoys strong support, particularly in rural northern Thailand.
Caretaker Prime Minister Niwattumrong Boonsongpaisan, who replaced Yingluck, did not take part in the political talks and has refused calls to step down.
The pro-Thaksin “Red Shirt” movement had called for new national polls they hope will provide a fresh mandate to the beleaguered elected government.
But the anti-government protesters who have waged a debilitating protest campaign for seven months are demanding vague political reforms first.
The reforms are widely seen as a bid to cripple the political power of Thaksin’s family and allies.
