Princess Bajrakitiyabha is being treated at Bangkok’s Chulalongkorn hospital after losing consciousness, royal palace says.

The Thai King Maha Vajiralongkorn‘s eldest child has been hospitalised due to a heart problem, the royal palace says.

Princess Bajrakitiyabha, 44, lost consciousness early on Wednesday while she was attending a working dog championship organised by the army in northeastern Nakhon Ratchasima province of Thailand

She was flown by helicopter to Bangkok after her condition stabilised, the palace said in a statement, without elaborating.

The princess was being treated at Bangkok’s Chulalongkorn hospital on Thursday where she is undergoing treatment and checkups.

Princess Bajrakitiyabha, known in Thailand as “Princess Bha”, is one of King Vajiralongkorn’s three children who have formal titles, making her eligible for the throne

King Vajiralongkorn has yet to formally designate an heir and there has been no official discussion on the prospect of the princess taking the throne.

She has worked with the United Nations and served as Thailand’s ambassador to Austria, Slovenia and Slovakia.

There have been protests against the Thai monarchy in recent years, calling for curbs on the king’s powers. Vajiralongkorn became king in 2016 December after his father King Bhumibol Adulyadej died.