The palace says King Maha Vajiralongkorn, ascended the throne following the October death of his widely revered father Bhumibol Adulyadej.
Bangkok: Thailand's king will sign off on the country's new constitution later today, a document touted by the junta as a cure for political instability but dismissed by critics as a move to further entrench army influence.
The military says royal approval of the charter -- Thailand's twentieth since 1932 -- will open the door for the restoration of elections following their last coup in 2014.
But opponents say the new charter means any polls, whose date keeps slipping, will only offer Thais a form of neutered democracy with a fully appointed senate and tough controls on elected lawmakers.
The palace says King Maha Vajiralongkorn, who ascended the throne following the October death of his widely revered father Bhumibol Adulyadej, will sign the document at a televised ceremony in Bangkok on Thursday afternoon.
Vajiralongkorn surprised many earlier this year by ordering rewrites to parts of the charter that deal with his powers.
In a sign of the opacity surrounding all things royal, authorities have yet to release the wording of those new sections and it is unclear if they will be published before the charter is signed.
Thailand has stumbled through more than a decade of political instability that has hampered growth in what was once one of the region's fastest growing economies.
In a period dubbed "the lost decade" Thais witnessed repeated rounds of deadly protests, a string of short-lived governments and two military coups.
Analysts say the latest constitution harks back to the Cold War-era when Thailand's elected lawmakers were often kept in check by unelected bodies and committees in what many called "guided democracy".
Thitinan Pongsudhirak, a politics expert at Chulalongkorn University, said the document is a far cry from Thailand's most liberal charter, the 1997 so-called "People's Constitution".
"The new charter reverses progress on people's representation that culminated with the 1997 constitution after the military was disgraced in 1992 for being a dictatorship and shooting pro-democracy protesters," he told AFP.
"Now appointments are back en masse at the expense of elected representatives." The kingdom's political split broadly pits rural and poor supporters of ousted premiers Thaksin and Yingluck Shinawatra versus a military-backed Bangkok middle class and business elite.
Shinawatra-linked parties have won every election since 2001. Their opponents accuse them of corruption and damaging populist policies.
In addition to an appointed upper house, the new constitution will bolster powers of the country's interventionist constitutional court and make it easier to impeach a civilian leader.
The military says the charter will help purge Thailand of corrupt civilian politicians and raise the possibility of elections being held by mid-2018 once it is signed.
They have also said they will draw up a "20-year plan" for the country that any future government will be bound to follow.