Thailand's junta said Friday that it would keep control of national security under a planned interim government, despite international calls for a return to full civilian rule.

The junta, formally known as the National Council for Peace and Order (NCPO), will remain in place alongside a government that is set to be appointed by September, army chief General Prayut Chan-O-Cha said.

"The government will focus on administration while the NCPO will concentrate on its responsibility for security," Prayut, who led a May 22 coup that overthrew an elected government, said in a weekly televised address.

The new cabinet is expected to be picked by a junta-appointed national assembly which army sources say is expected to be stacked with military officers.

The junta has ruled out holding new elections before around October 2015, despite appeals from the United States and the European Union for a return to democracy.

The Thai military seized power after nearly seven months of protests saw 28 people killed and paralysed the government of former prime minister Yingluck Shinawatra.

It was the latest chapter of a long-running political crisis broadly pitting Yingluck's billionaire family and its supporters against a royalist establishment backed by parts of the military and judiciary.

The army said the takeover was necessary to restore order.

But critics accuse the junta of using political unrest as an excuse for a power grab in order to curb the political dominance of Yingluck's elder brother, the fugitive former premier Thaksin Shinawatra.

The military has imposed martial law, banned public rallies, censored the media and summoned several hundred people for questioning, while also seeking to win public support with free concerts and a vow to crack down on corruption.