Princess Bajrakitiyabha Mahidol has been unconscious in hospital since falling ill due to heart problems in December 2022 during a dog training session.

The Bureau of the Royal Household gave the first update on her condition in more than two years on Friday, saying she had suffered a “severe” blood infection.

A second update issued today said doctors were closely monitoring her condition.

“The medical team said that she remains in a state of low blood pressure, requiring continuous treatment,” the statement from the Bureau of the Royal Household said.

“Doctors are administering medication to stabilise her blood pressure, along with medical equipment and antibiotics to support kidney function and breathing.”

Known in Thailand as “Princess Bha”, the 46-year-old is the eldest daughter of King Maha Vajiralongkorn and the only child from his first marriage.

Educated in Britain, the US and Thailand, Bajrakitiyabha has held a number of positions with the United Nations and has campaigned for better treatment of women in prisons.

She is seen as close to her father, and was appointed to a senior role in his bodyguard command a year before her hospitalisation.

The 73-year-old king, who has seven children from four marriages, has not announced his chosen heir, though succession rules favour men.

Strict rules govern what can and cannot be said about the Thai royal family, who are protected from criticism by lese-majeste laws which carry prison sentences of up to 15 years per charge.