The kingdom’s nine-member constitutional court ruled that Prayut was not guilty of conflict of interest by living in an army residence after leaving the military.
“The status of General Prayut Chan-O-Cha as prime minister and defence minister remains unchanged,” the head judge said.
The court ruled that Prayut’s status as prime minister entitled him to live in the house even though he stepped down as army chief in 2014.
The ruling, though widely expected, is likely to inflame the protest movement that has shaken Thailand since July calling for Prayut, who came to power in a coup, to quit.
As the judgment was read out, pro-democracy protesters massed for a fresh rally at a major intersection in northern Bangkok.
“I’m not surprised because I think the court received the directive from the top and the court is not fair,” Reeda, 26, a graduate student, told AFP as demonstrators gathered at Lat Phrao intersection.
“In the past they always decide decisions that contrasts with the feeling of the people.”
The judge said the military had changed the status of the residence from an army house to an guest house in 2012 “so technically, the defendant’s no longer living inside an army house”.
The main opposition party Pheu Thai brought the legal challenge, which if it had succeeded would have forced Prayut and his cabinet out of office.
The premier has previously argued his family must stay at the army house on a military base for security reasons.
He appeared relaxed yesterday ahead of the decision, saying he would send his lawyers to the court but would not go in person.
“If the court rules that you’ve done wrong then you’ve done wrong... if not then that’s the end of the story,” he told reporters in Bangkok.
Some critics say the constitutional court is unduly interventionist.
Titipol Phakdeewanich a political scientist with Ubon Ratchathani University, said Prayut’s victory was little surprise.
“They always try to find a legal loophole to protect him,” he told AFP.
Chulalongkorn University political scientist Thitinan Pongsudhirak echoed the view.
“Anyone who’s followed Thai politics for the past 15 years will think it’s a foregone conclusion... because the constitutional court has been so politicised since 2006 that it does not engender public trust,” he told AFP.
The pro-democracy movement is facing legal action of its own, with five key leaders charged on Monday under Thailand’s strict royal defamation laws — the first time they have been used in two years.
As well as calling for Prayut to go, protesters also want reforms to the army-drafted constitution and for changes to the monarchy — a taboo-smashing demand in a country that has long revered its royal family. — AFP