Thailand's coup leader General Prayuth Chan-ocha was appointed prime minister on Thursday by a legislature he hand-picked, giving the army chief a veneer of legitimacy even while the military presses on with efforts to silence its critics.

The army seized power on May 22 in a bloodless coup following six months of sometimes deadly street protests that contributed to the ousting of Prime Minister Yingluck Shinawatra, whose populist government was opposed by the Bangkok royalist establishment.

Although Prayuth's appointment paves the way for an interim government to be set up in the coming weeks, power will remain firmly in the junta's hands. The general has said he plans to press ahead with a year of political reforms before a new election that he said will take place by late 2015.

"It is designed to give him the power to run the country according to the law. The premier position will give him legal power in the Thai governance system," Gothom Arya, a lecturer in human rights studies at Mahidol University, told Reuters.

The nomination comes as no surprise - the National Legislative Assembly (NLA) that chose Prayuth is largely considered little more than a rubber stamp parliament tasked with enacting sweeping reforms under the army's watch.

The 60-year-old Prayuth will retire as army chief in September but will stay on as head of the junta, formally known as the National Council for Peace and Order. His appointment will need to be endorsed by Thailand's king.