The Thai king's eldest daughter has died at the age of 47 after a prolonged illness, the royal palace said in a statement.

Thailand's Princess Bajrakitiyabha has passed away in a hospital after being in a coma for over three years, the royal palace announced on Friday. She was 47 years old.

The princess was suffering from an abdominal infection and "her condition continued to worsen", the palace said.

Bajrakitiyabha was the eldest daughter of Thailand's king, Maha ​Vajiralongkorn.

In December 2022, while on a visit to the northeastern province of Nakhon Ratchasima, the princess suddenly lost consciousness due to a heart condition.

She was flown by a helicopter to the capital Bangkok for treatment and had been hospitalized since then.

The palace said she "passed away peacefully" on Thursday evening.

Her body will lie in state at the Grand Palace in Bangkok, the royal palace said, adding that the funeral would be held "with the highest honors according to royal tradition."

The Thai government is also expected to declare a period of national mourning.

Who Was Thailand's Princess Bajrakitiyabha?

Popularly ​known as Princess Bha, Bajrakitiyabha was the only child from King Vajiralongkorn's first marriage to Thai Princess Soamsawali.

She was born on December 7, 1978, when Vajiralongkorn was still the crown prince.

The princess played a very active role in Thailand's public life, and served as a prosecutor and a diplomat after securing a master's degree in law from Cornell University in the United States.

She undertook several justice reform efforts, including on the issues of the living conditions and rehabilitation of incarcerated Thai women.

In her diplomatic career, Bajrakitiyabha was appointed as an honorary United Nations goodwill ambassador for women and for the Office on Drugs and Crime.

She served as Thailand's ambassador to Austria from 2012 to 2014.

"I ask myself now, what am I exactly? A prosecutor? A criminal lawyer? A diplomat? The answer is everything all together. I say I am a hybrid," the princess said on a visit to her New York law school, according to the Cornell Chronicle.