Jatupat Boonpatararaksa was arrested in December for sharing on Facebook a profile of King Maha Vajiralongkorn.
Criticising the royal family is punishable by up to 15 years in prison per count in Thailand, where the law is broadly-interpreted and aggressively enforced.
Scores of lese majeste cases have been brought against members of the public and activists in recent years, often for comments made online.
Jatupat, better known by his nickname Pai, was indicted by a court in northeastern Khon Kaen province Friday, his lawyer Krisadang Nacharut told AFP.
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While thousands shared the article, Jatupat -- a prominent critic of the country's military junta -- is the only person to have been prosecuted so far.
The 25-year-old law student had already been detained for more than 50 days, after judges rejected multiple requests for his release on bail in closed-door hearings.
The UN this week expressed concern over the secret proceedings and called for Thailand to repeal the lese majeste law.
Observers are closely watching whether the new monarch endorses or backs away from the royal defamation law.
The lese majeste law effectively bars public scrutiny of key royal figures, spawning a culture of self-censorship across media, academia and arts.
The profile shared by Jatupat contained details of 64-year-old Vajiralongkorn's personal life that are well-known inside the kingdom but rarely printed by the Thai press.
The new king has spent much of his life abroad and does not enjoy his father's widespread popularity.
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