Influential former Thai prime minister Thaksin Shinawatra, a powerful backer of the ruling government, has been formally indicted for allegedly insulting the monarchy in a 2015 media interview.

It is the first of four high-profile cases involving key political players that are before the courts on Tuesday, in the latest legal wrangling that could see Southeast Asia’s second-largest economy plunged into a new period of uncertainty.

The cases involve some of Thailand’s most powerful politicians, including its current prime minister, and could deepen a decades-old rift between the conservative-royalist establishment and its opponents, such as the populist ruling Pheu Thai party and the opposition Move Forward party.

“The prosecutor has sent the suspect to court,” Prayuth Bejraguna from the Attorney General’s office said, referring to the 74-year-old Thaksin.

Thaksin, who denies any wrongdoing, could face pre-trial detention if he is denied bail by a criminal court, following the indictment.

Thailand’s lese-majeste law, one of the world’s toughest, carries a maximum jail sentence of up to 15 years for each perceived royal insult.

Separately, the Constitutional Court will conduct a hearing in a case lodged by a group of senators that could potentially mean Prime Minister Srettha Thavisin is dismissed from office for breaching the law in appointing a lawyer with a conviction record to his cabinet.

The same court will also hear a case seeking to disband the popular opposition Move Forward Party for its campaign to amend the country’s royal insult law, following a complaint by the Election Commission.

The court is expected to announce the next hearing or verdict date for cases involving Srettha and Move Forward on Tuesday.

The Constitutional Court will also rule whether the ongoing selection process for a new upper house, which started earlier this month and is scheduled to conclude in early July, is lawful.

If the court cancels or delays the process, it would temporarily extend the term of military-appointed senators who have a played crucial role in the formation of the previous government.

-AAP