(Adds Suthep released on bail)
By Martin Petty and Panarat Thepgumpanat
BANGKOK, May 26 (Reuters) - Thai coup leader General Prayuth Chan-ocha will receive the endorsement of King Bhumibol Adulyadej on Monday as head of a ruling military council, and the general will then give his first address to the nation since seizing power last week.
The royal command ceremony, a significant formality in a country where the monarchy is the most important institution, was due begin at 10:49 a.m. (0349 GMT), the army said. It gave no reason for that time, but it is likely it was deemed auspicious.
Prayuth's address is likely to be viewed with conflicting attitudes in a country polarised by nearly a decade of rivalry between the royalist establishment, of which Prayuth is a member, and a populist politician who broke the political mould.
Prayuth will outline steps he intends to take, including the proclamation of an interim constitution and the setting up of a legislative council, the military said. It did not elaborate.
The military said it seized power last Thursday to end six months of sometimes violent protests against the populist government of Prime Minister Yingluck Shinawatra.
But it has taken over with a heavy hand, detaining perhaps scores of people, most allied with Yingluck's government, throwing out the constitution, dissolving the Senate and censoring media. Anyone who insults the monarchy or violates the military's orders will be tried in a military court.
Despite warnings, small crowds of people voicing opposition to the May 22 coup have been gathering in Bangkok as well as in the north and northeast, strongholds of the ousted government.
About 1,000 people thronged around Victory Monument, a central Bangkok hub, on Sunday, occasionally confronting lines of soldiers with riot shields, but there have been no clashes.
The military has relaxed restrictions on Yingluck, allowing her to go home although she is under military supervision.
"She is free to come and go as she pleases but will have to inform us as a sign of mutual respect and we will have soldiers guarding her home," a senior military official, who declined to be identified, said on Sunday.
Suthep Thaugsuban, who led the Bangkok protests that undermined Yingluck's government from last November, was released from army custody on Monday but taken with 12 associates to the Attorney General's office. Suthep faces a charge of insurrection relating to the protests but was granted bail, said a member of his legal team.
The easing of restrictions on Yingluck will do little to dispel concern among her supporters that the military is intent on a crackdown for reasons other than restoring order and ending antagonism between protesters backed by the establishment and the real power behind her government, her brother and former premier Thaksin Shinawatra.
Thaksin was ousted in a 2006 coup after big-spending policies had won him the passionate support, and votes, of the poor but the animosity of the establishment, who saw him as a corrupt, authoritarian opportunist and a threat to the old order.
Thaksin was also accused of being disrespectful to the monarchy and even a closet republican, which he denied.
The former leader has said on Twitter he was saddened by the latest events, and called on the army to treat everyone fairly. Thaksin has lived in self-exile since a 2008 graft conviction.
The crisis between the establishment and Thaksin comes amid anxiety over the issue of royal succession. The king, the world's longest-reigning monarch, is 86 and spent the years from 2009 to 2013 in hospital.
Crown Prince Vajiralongkorn does not command the same devotion as his father, but some Thaksin supporters have recently been making a point of showing their loyalty to the prince.
Meanwhile, one Thaksin ally, ousted Education Minister Chaturon Chaisang, said he expected the military to implement steps aimed at sidelining once and for all Thaksin, his family and his allies, and blocking forever his formidable political machine, which has won every election since 2001.
"Any election after that would be meaningless," Chaturon told Reuters by telephone from an undisclosed location on Sunday, referring to changes he expects the military to implement.
"The system will be designed so no matter which party people vote for, it won't be able to form a government."
For now, the military is focusing on getting the economy back on track and ending dissent.
Shares in building contractors jumped more than 3 percent on Monday on expectations the new military government would speed up disbursements for infrastructure projects that were put on hold during the months of political unrest.
Among them, Italian-Thai Development Pcl, the country's largest construction firm, rose 0.5 percent even though the army has summoned its president, Premchai Karnasuta, to appear before it on Monday.
In its latest such order, it told 38 people to come in, including political associates of Thaksin and several big business allies of the former telecommunications tycoon. (Additional reporting by Amy Sawitta Lefevre, Khettiya Jittapong and Aukkarapon Niyomyat; Writing by Robert Birsel; Editing by Alan Raybould and Alex Richardson)