Thai temples held prayers and senior leaders including the prime minister visited a hospital on Friday to wish a quick recovery for the eldest child of King Maha Vajiralongkorn, who collapsed earlier in the week with a heart condition.
Princess Bajrakitiyabha, 44, lost consciousness early on Wednesday in the northeastern province of Nakhon Ratchasima and was flown by helicopter to Chulalongkorn hospital in Bangkok after her condition stabilised "to a certain level", the palace said in a statement on Thursday.
There was no further official update of her condition on Friday.
Prime Minister Prayuth Chan-ocha and many senior officials, politicians and religious leaders visited Chulalongkorn hospital on Friday to lay orange flowers, the colour associated with the princess, and sign a book of well wishes.
Thailand's Buddhist Supreme Patriarch, Somdet Phra Ariyavangsagatayana has requested all Thai temples at home and abroad to conduct special daily chanting sessions for the princess, an official announcement from the National Office of Buddhism said.
The princess is one of three children of King Vajiralongkorn who has a formal title, making her eligible for the throne under a 1924 Palace Law of Succession and the country's constitution.
The king has yet to formally designate an heir since becoming king in 2016, and there has been no official discussion on the prospect of the princess taking the throne.
(Reporting by Panu Wongcha-um and Athit Perawongmetha; Editing by Kanupriya Kapoor)