A criminal court in Thailand will decide on Friday whether former leader Thaksin Shinawatra violated the country’s strict lese-majesty law, the first of three court cases that could decide the fate of one of the country’s most powerful families.

Thaksin is accused of insulting the monarchy during an interview with South Korean newspaper Chosun Ilbo in 2015.

He has denied wrongdoing and repeatedly pledged his loyalty to the king, who according to the constitution should be “enthroned in a position of revered worship”.

Thailand has one of the world’s most severe lese-majesty laws, under which criticism of the monarchy is punishable by between three and 15 years in prison. Since 2020, at least 281 people have been charged under the law, which can be interpreted broadly, with protesters prosecuted for political speeches, wearing clothes deemed to be an impersonation of the royals, or for being involved in the sale of satirical cartoons. Critics say the law is used to target political opponents and silence dissent.

Friday’s case is one of a series of legal challenges facing Thaksin and his family, who have been locked in a power struggle with Thailand’s military royalist establishment for decades.

Next week, Thailand’s constitutional court will decide whether his daughter, suspended prime minister Paetongtarn Shinawatra, should be removed from office over a leaked phone call with Cambodia’s former leader Hun Sen, in which she discussed the two countries’ border dispute.

Thaksin also faces a separate court case over allegations he wrongly avoided prison on health grounds upon his return from self-imposed exile in 2023. Thaksin had spent more than 15 years abroad to avoid legal charges that he had previously said were politically motivated, but returned after striking a controversial deal with his former enemies in the military establishment – an arrangement that now appears increasingly fragile.

Thaksin, a billionaire businessman who once owned Manchester City football club, was first elected prime minister in a landslide victory in 2001, and he went on to build a strong voter base among rural communities in the north of Thailand by offering welfare and economic policies to improve people’s livelihoods.

However, he was also accused of corruption and human rights abuses, and was loathed by conservatives in Bangkok. He was ousted from power in a military coup in 2006. His sister Yingluck Shinawatra was removed from office by a court ruling followed by a coup in 2014.

Thailand’s courts have frequently intervened in politics, dissolving popular political parties and banning politicians from office.

The latest series of court cases is a stark reminder of the “imbalance in power relations between elected and unelected forces in Thailand”, said Dr Napon Jatusripitak, visiting fellow at ISEAS Yusof Ishak Institute. “This is not the first time that an unelected set of judges gets to decide a national outcome and veto whatever mandates were made by the Thai electorates,” he said.

However, he added that, while in the past, punitive court rulings against the Shinawatras elicited sympathy from their loyal support base, the family’s popularity has diminished significantly.

The deal Thaksin struck when he returned to the country – where he joined with their old military opponents in order to keep a popular pro-reform party out of office – had damaged his credibility, said Napon.

The party’s perceived failure to deliver on economic promises, and, most significantly, anger over claims Paetongtarn had kowtowed to Cambodia during a phone call with Hun Sen, has led to a further collapse in support.

Even if Thaksin survives Friday’s court ruling, Paetongtarn could be removed from office next week, potentially ushering in a new period of political instability in the country.