By Amy Sawitta Lefevre and Pairat Temphairojana
BANGKOK/KHON KAEN, Thailand (Reuters) - Thai voters approved a junta-backed constitution in a referendum on Sunday, preliminary results showed, an outcome that paves the way for an election next year but will also require future elected governments to rule on the military's terms.
Voters handed the junta led by Prime Minister Prayuth Chan-ocha a convincing win in its first major popularity test at the ballot box since it seized power in a 2014 coup.
With 94 percent of the vote counted, early results from the Election Commission showed 61.4 percent of Thais had voted for the charter, while 37.9 percent rejected it. Full results are due on Wednesday.
The junta says the constitution is designed to heal more than a decade of divisive politics in Thailand that has dented economic growth and left scores dead in civil unrest.
But Thailand's major political parties and critics of the government say the charter will enshrine the military's political role for years to come.
The win was a blow to the powerful Shinawatra clan and their allies, whose populist politics are reviled by Thailand's military-royalist establishment. Thaksin Shinawatra was ousted as prime minister in a coup in 2006 and his sister Yingluck's government was toppled by Prayuth in 2014.
The acting head of the Peau Thai Party, which carried Yingluck to power, said Thais may have voted pragmatically for the charter as the fastest route to an election.
"The reason most Thais accepted the constitution is because they want to see a general election quickly," Wirot Pao-in told reporters at the Peau Thai's Bangkok headquarters on Sunday. "All sides must now help move the country forward."
Across town at the United Front of Democracy Against Dictatorship group, the tone was less conciliatory.
"What will we do next? Tell Prayuth that, although it seems he is winning, this is not a victory he can be proud of because his opponents have not been able to fight at their best due to threats and harassment," said Jatuporn Prompan, chairman of the pro-Shinawatra UDD.
Some people wept as the result became clear at the UDD headquarters in Bangkok.
The junta, formally known as the National Council for Peace and Order (NCPO), banned debate about the constitution and campaigning ahead of the vote. The authorities have detained and charged dozens of people who have spoken against it, including politicians and student activists.
"(It was) a one-sided campaign in which the junta indirectly encouraged 'yes' votes and arrested or intimidated referendum opponents," said Paul Chambers, director of research at the Institute of Southeast Asian Affairs in the city of Chiang Mai.
"As a result many voters did not show up while others felt compelled to vote 'yes'."
Turnout of around 55 percent was below the 80 percent targeted by the Election Commission. That likely favored the government, said Thithinan Pongsudhirak, director of the Institute of Security and International Studies at Bangkok's Chulalongkorn University.
"This is a hands-down convincing margin of approval for the military government," he said. "This is going to give the junta a signal to go full steam ahead for elections next year. They will feel confident from this vote about rolling out their plans for the transitional period."
Around 200,000 police were deployed for the referendum and voting passed without major incident.
The yes vote will likely be cheered by Thai financial markets.
"The outcome is our best case scenario and investors should react positively as it's clear that the election will happen next year," said Kasem Prunratanamala, head of research at CIMB Securities.
"Foreign investors had been waiting for the vote and may invest more now."
DECADE OF TURMOIL
The vote comes amid concerns about the health of King Bhumibol Adulyadej, 88. The military has for decades invoked its duty as defender of the deeply revered monarch to justify its interventions in politics.
Critics say the charter is the military's attempt to make good on their failure to banish Thaksin from Thai politics after the 2006 coup.
Senior army officers have told Reuters the new charter aims to make future coups unnecessary by weakening political parties and ensuring the military a role in overseeing Thailand's economic and political development.
Under the constitution, which would be Thailand's 20th since the military abolished an absolute monarchy in 1932, a junta-appointed Senate with seats reserved for military commanders would check the powers of elected lawmakers.
Thaksin called the charter a "folly", saying it would perpetuate the junta's power and make it impossible to govern Thailand.
Thaksin retains strong influence despite living in self-imposed exile. His support base in the rural northeast bucked the trend and voted against the charter on Sunday.
Decha Shangkamanee, a day laborer in Khon Kaen, said he had voted against it because he disliked the junta, but did not expect the referendum to make much difference.
"I know that nothing really changes today with the way the country is ruled," he said.
(Additional reporting by Aukkarapon Niyomyat, Orathai Sriring, Panarat Thepgumpanat, Patpicha Tanakasempipat and Simon Webb; Writing by Amy Sawitta Lefevre and Simon Webb; Editing by Lincoln Feast, Gareth Jones)