The announcement came from junta chief Prayut Chan-O-Cha, who had promised immediately after his May 2014 coup to return power to civilians within 18 months.
That date has repeatedly slipped, and even after the vote critics say there will be limits on democracy under a new military-scripted charter.
"In November 2018 there will be an election. Is it clear?" the often gruff leader told reporters, adding that he would announce the exact date next June.
He said he would also "consider the timing for relaxing conditions on political parties at the appropriate time".
All politics and protests have been banned under Prayut's regime, the most autocratic Thailand has seen for a generation.
The election will not restore the same level of democracy that existed before the latest military takeover in Thailand -- a country that has seen more than a dozen coups since the end of absolute monarchy in 1932.
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After seizing power the generals drafted a new charter that curbs the power of elected politicians and calls for a fully appointed Senate or upper house, with several spots reserved for military leaders.
It also strengthens the constitutional court, a frequent thorn in the side of elected governments, making it easier to impeach a civilian leader.
The junta has further enshrined its governmental role by declaring that any future administration must adhere to its "legally binding 20-year-plan" for the country.
Prayut travelled to the US earlier this month to meet President Donald Trump at the White House -- an encounter he was denied under Barack Obama's administration.
A joint statement after the meeting said Trump welcomed Thailand's commitment to "lead to free and fair elections in 2018".
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That unexpected announcement caused a commotion back in the kingdom, where Prayut initially rowed back and said only that a specific date would be announced in 2018.
He also said that Trump did not ask about political developments during their encounter.
The junta has defended its takeover and its new charter -- Thailand's twentieth since 1932 -- as necessary to curb the political unrest that has rocked the nation for over a decade.
But critics say the military is far from being a neutral player and is bent on crippling the political clan led by ousted premiers Thaksin and Yingluck Shinawatra, whose parties have won every poll since 2001.
After her government was toppled in the 2014 coup, Yingluck was put on trial for negligence over a costly rice subsidy scheme -- a case which her supporters slammed as a junta-led witch hunt.
The former premier fled Thailand in August before the court delivered its verdict and sentence -- a five-year jail term that effectively spells the end of her political career.
Thaksin, who was overthrown in a 2006 coup, is also living in self-exile to avoid convictions which he says are politically motivated.
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