By Panarat Thepgumpanat and Patpicha Tanakasempipat
BANGKOK (Reuters) - Thailand's king signed a military-backed constitution into law on Thursday, an essential step toward an election the junta has promised will restore democracy after the 12th successful coup in little over 80 years.
The new constitution is the Southeast Asian country's 20th since the end of absolute monarchy in 1932 and critics say it will still give the generals a powerful say over Thai politics for years, if not decades.
King Maha Vajiralongkorn's power was also reinforced by recent changes made at the palace's request to the draft constitution approved in a referendum last August, analysts said.
"May the Thai people be united in following and protecting the constitution to maintain democracy and their sovereignty," an officer with the Royal Scribes Bureau said at the glittering palace ceremony. He spoke on behalf of the king, a former army officer who signed the constitution in dress uniform.
Prime Minister Prayuth Chan-ocha, who took power in the 2014 coup, said Thailand was now on course to an election within the 19 months set by the constitution - although because a number of steps are involved, he cannot set an exact date.
"Once a new government is formed, this government will hand over its duties and cease its term," he said on state television.
The army initially promised an election in 2015, after seizing power from a government run by Yingluck Shinawatra, sister of Thaksin Shinawatra, a populist leader ousted in 2006. The army said the coup was to end political turmoil.
Thailand's main political division remains between a Bangkok-based, strongly royalist and pro-army elite and poorer supporters of the Shinawatras' movement, particularly from the rural north and northeast.
Ousted Prime Minister Yingluck's Pheu Thai Party said it was more optimistic about election prospects after the king endorsed the constitution.
"With the constitution in place, an election seems more a reality," Chavalit Vichayasuthi, its acting deputy secretary-general, told Reuters.
The government should lift a ban on political activities so parties can campaign, said Abhisit Vejjajiva, a former prime minister and leader of Thailand's other key political party, the Democrat Party.
"We are ready for the election," he said. "We still aren't allowed to hold meetings, but we're doing what we can."
One of the most controversial provisions of the new constitution is for the outgoing military government to appoint a senate that will have a say in appointing the prime minister.
The junta has argued the measure is necessary to prevent coups in a transition period after the election.
Thais approved the outline of the new constitution in a referendum last August but the palace requested changes in January after King Vajiralongkorn took over from his revered late father, King Bhumibol Adulyadej, who had ruled for more than seven decades.
Six changes had been made to the constitution published in the Royal Gazette on Thursday.
One change allows the king to travel abroad without appointing a regent. The king has spent much of the past few years in Germany, where he has a son in school.
Another change was the removal of a clause giving power to the constitutional court and other institutions in the event of an unforeseen crisis. Removing it underlined the king's role.
"In practice, the king will have more say, more power," Kan Yuenyong, executive director of think-tank Siam Intelligence Unit, told Reuters.
Thursday was a public holiday to mark the establishment of the Chakri dynasty 235 years ago. The current king is also known as King Rama X in the dynasty.
(Reporting by Panarat Thepgumpanat and Patpicha Tanakasempipat; Writing by Matthew Tostevin; Editing by Clarence Fernandez and Catherine Evans)