The eldest child of Thailand’s King Maha Vajiralongkorn has died aged 47, the palace has said, after nearly four years in a coma.

Princess Bajrakitiyabha Mahidol, known in Thailand as Princess Bha, had been in hospital since December 2022 when she became gravely ill after having heart problems while out training her dogs.

There had been few updates regarding her health since her hospitalisation, though in early May the palace said her medical condition had worsened as a result of multiple infections in several organs and physicians were unable to stabilise her irregular heart rate.

In April, physicians discovered a stomach infection that led to inflammation in her intestines, causing her blood pressure to fall and her heartbeat to become irregular. Her kidney function and breathing had been supported through medical equipment, palace statements said.

Born in 1978 to then-Crown Prince Vajiralongkorn and his wife, and cousin, Princess Soamsawali, Bajrakitiyabha held several degrees, including a doctorate from Cornell University. She served as an ambassador to Austria, as well as in the attorney general’s office, the royal security command, and as a goodwill ambassador to the UN office on drugs and crime. Bajrakitiyabha also campaigned for the rights of female prisoners.

Her death will raise questions about succession – a sensitive issue in Thailand where public discussion of the monarchy is limited by a strict lese majesty law. Criticism of the royal family can lead to up to 15 years in prison on a single charge.

Bajrakitiyabha was considered by many analysts to be a well-suited heir to the throne, though this has never been addressed officially.

The king has married four times and has seven children. Bajrakitiyabha was one of only three of his children to hold a royal title, along with Princess Sirivannavari, 38, and Prince Dipangkorn, 20.

Some had speculated that Bajrakitiyabha may have acted as a regent for Dipangkorn, who is reported to have learning difficulties, or become queen herself. Thailand has never had a ruling queen.

Vajiralongkorn’s four others sons have lived abroad since the mid-1990s after he announced his divorce from their mother, Sujarinee, a former actor, publicly accusing her of adultery. Their sister Princess Sirivannavari was returned to Thailand and raised as a member of the royal family.

The estranged sons travelled to Thailand for the first time in decades in 2023, and made several visits to the country until, in 2025, they claimed they had been denied entry to Thailand.

The king divorced Bajrakitiyabha’s mother in 1991 but she retains a royal title and is a key member of the monarchy. Dipangkorn’s mother, Srirasmi Suwadee, was stripped of her royal title after her family were accused of corruption.