Separately, the Constitutional Court set July 3 and July 10, respectively, as the next hearing dates for two cases involving the opposition Move Forward party and the incumbent prime minister Srettha Thavisin.
It also ruled that an ongoing selection process for a new upper house, which started earlier this month, is lawful, clearing the deck for 200 new lawmakers to take over from a military-appointed senate later this year.
The quartet of court cases has put Thai politics and markets on edge, raising the spectre of instability in Southeast Asia's second largest economy that has struggled to shift gears since it was battered by the COVID-19 pandemic.
Srettha, a real estate tycoon who entered politics with the ruling Pheu Thai party last year, faces potential dismissal over the appointment of a lawyer who was imprisoned for contempt of court to his cabinet.
The case was brought on by a group of 40 conservative military-appointed senators who complained to the Constitutional Court against Srettha. The prime minister denies the charge.
Move Forward, which won last year's election but was blocked by conservative lawmakers from forming the government, was taken to court by the election commission over its campaign to amend Thailand's royal insult - or lese majeste - law under article 112 of the criminal code.
The party denies any wrongdoing.
The lese majeste law is also at the heart of the legal proceedings against Thaksin, who returned to Thailand last August after 15 years in self-imposed exile following his ouster from power by a military coup.
He is accused of violating the law, which carries a maximum jail sentence of up to 15 years for each perceived royal insult, during a media interview in 2015.
"He did not commit any wrongdoing and did not defame anyone protected by article 112," Thaksin's lawyer Winyat Chatmontre told reporters, adding that Thaksin has pleaded not guilty.
The billionaire successfully secured bail from the Criminal Court of Thailand soon after the attorney-general formally indicted him earlier on Tuesday.
"The court has released Thaksin on bail of 500,000 baht ($A20,546) under the condition that he is prohibited from leaving the country unless granted permission," a court statement said.
Thailand's politics for decades has been defined by a relentless struggle between the conservative-royalist establishment that is backed by the military and its opponents, such as Pheu Thai and Move Forward.
This rift has previously triggered violent street protests, dissolutions of political parties, airport closures and military coups that have hamstrung the Thai economy.
The court decisions on Tuesday gave the conservative establishment the upper-hand in dealing with their opponents, said Titipol Phakdeewanich, a political science professor at Thailand's Ubon Ratchathani University.
"The lese majeste case will continue to hang over Thaksin while the judgments for the prime minister and Move Forward are still quite a long way off, giving more time for the conservative establishment to come up with ways to deal with their perceived threats," he said.
The ruling Pheu Thai is backed by Thaksin and his deep-pocketed family, which has been the catalyst behind political parties that have won all but one election since 2001.
Three Shinawatra governments have been toppled by coups or court rulings.
