BANGKOK - Thailand's military makes way for a new administration in coming weeks, but the generals will keep a tight grip on power by filling an interim cabinet and legislature with soldiers, military sources said on Wednesday.

The armed forces took power on May 22 in a bloodless coup following six months of street demonstrations that contributed to the ousting of Prime Minister Yingluck Shinawatra. The junta has since purged officials linked to Yingluck and her brother, Thaksin, a former premier himself and widely seen as the power behind Yingluck's government.

The commander who led the May 22 coup, General Prayuth Chan-ocha, will likely to become prime minister to head a cabinet of staunch loyalists, the sources said. That will ensure that he has direct control of sweeping reforms that the military wants the interim cabinet and legislature to enact.

The transition, mapped out in an interim constitution promulgated last week, retains the junta, or National Council for Peace and Order (NCPO), and offers it immunity and broad powers to overrule the interim government and a 220-member National Legislative Assembly (NLA) that it will appoint.

"He's already been performing duties like a prime minister," an army source said of Prayuth, requesting anonymity because he was not allowed to speak about the issue to the media.

"Being both prime minister and head of NCPO will make the transition before elections more effective and more accurately reflect the goals of the NCPO to reform the country."

The junta says reform is needed to end years of political instability and prevent a repeat of the six months of sometimes violent protests that paralysed Yingluck's government. It has said elections will be held late next year.

Some analysts and supporters of the ousted government say the military reforms will echo the goals of the protesters and are aimed at eroding the power of the billionaire Shinawatra family, which controls a populist political machine that has won every election since 2001 with rural and working-class backing.

The interim constitution provides a framework for stringent political control last exercised by the military in 1970s and 1980s, when it oversaw an era of military-managed democracy after a succession of coups and weak coalition governments.

The military is keen to prevent a repeat of the mistakes of its 2006 putsch and 2007 constitution re-write. Both failed to weaken the influence of the self-exiled Thaksin, the nemesis of the army-backed royalist establishment.

Thaksin's governments have been toppled three times by coups or courts since 2006, interventions his allies say were orchestrated by a conservative oligarchy threatened by his clique of upstart businessmen.

Sweeping power

Critics have condemned the constitution, particularly article 44, allowing the NCPO to overrule the NLA in matters it deems "destructive to the peace and safety of the country".

New York-based Human Rights Watch has spoken out against alleged abuses and widespread detentions of supporters of the ousted government and last week said the constitution gave the junta "sweeping and unaccountable power" and "unchecked authority to do almost anything it wants".

That has even alarmed some in the opposition Democrat Party, which would stand to gain from any weakening of Thaksin's grip.

"Personally, I think section 44 is like a gun," its deputy leader, Nipit Intrasombat, told Reuters. "It can be used to defend yourself and others, but it can also be used to harm."

Wissanu Krea-ngam, the junta's legal adviser, last week defended the constitution, saying the NCPO would be criticised if it let the coup "be a waste amounting to nothing".

"It's necessary for this interim constitution to have some rules that may seem strict and rash," he said in a televised statement.

The NCPO will pick members of the legislative assembly, which is expected to convene next week. The assembly will appoint a prime minister to choose a 35-member cabinet, which Prayuth says would be formed in September.

Several military sources say the assembly will have a strong armed forces contingent, with half the chamber either serving or retired members of the military. Prayuth is expected to grant cabinet portfolios to NCPO members.

Another military source said members of Prayuth's politicised military clique, the "Eastern Tigers" of the Queen's Guard, would take cabinet posts, including retired former army chief Anupong Paojinda as deputy prime minister and defence minister.

Air Chief Marshall Prajin Juntong, the junta's economic tsar, could be appointed energy or transport minister, General Narong Pipatthanasai education minister and armed forces chief Thanasak Patimaprakorn deputy premier, according to the sources.

Former central bank governor Pridiyathorn Devakula would return as post-coup finance minister. He formed part of the administration after the 2006 coup but quit after introducing capital controls that spooked investors and led to a 15-percent stock market slump, its biggest ever one-day fall.