Princess Bajrakitiyabha Narendira Debyavati, known as Princess Bha, died aged 47 on Thursday following an abdominal infection.
She had already spent more than three years in a coma due to a cardiac condition.
People queued nearby for their turn to perform a Buddhist ritual of pouring holy water into a ceremonial bowl placed before a portrait of the princess.
Thousands of mostly older mourners sat in sweltering temperatures along the 10-kilometre route to the Grand Palace from Chulalongkorn Hospital, where the princess had been treated.
Her body arrived at the palace at around 5:00 pm local time in a solemn and orderly procession.
Police closed roads and traffic ground to a halt in parts of Bangkok’s commercial centre as the royal motorcade passed, led by King Maha Vajiralongkorn and Queen Suthida.
Thailand’s public broadcaster Thai PBS reported that the princess’s body was carried in the same vehicle that had transported the body of her grandfather, King Bhumibol, who died in October 2016.
Live footage broadcast by a public television station showed monks chanting before the king and queen, who were seated on gilded chairs with a portrait of the princess behind them.
The Thai government has yet to announce details of the funeral, but it has instructed state officials to wear black and ordered that flags be flown at half-mast for 15 days.
The proceedings were carried out under tight security and strict protocol, with attendants wearing formal attire, media access restricted and dozens of police officers standing guard. (AFP)
