Their Majesties the King and Queen on Friday visited Her Royal Highness Princess Bajrakitiyabha Narendiradebyavati at King Chulalongkorn Memorial Hospital where she is being treated after losing consciousness due to heart problems on Wednesday while exercising her dogs.
Thais nationwide are praying for her speedy recovery.
Separately, Her Royal Highness Princess Sirivannavari Nariratana Rajakanya also visited the princess at the hospital on the same day.
Her Royal Highness Princess Maha Chakri Sirindhorn, Her Royal Highness Princess Chulabhorn Krom Phra Srisavangavadhana, and Princess Ubolratana assigned their representatives to take flowers to the princess.
According to a statement by the Bureau of the Royal Household on Thursday, Princess Bajrakitiyabha passed out while training her pet dogs at 6.20pm in Nakhon Ratchasima's Pak Chong district on Wednesday.
The dogs were being trained as they are slated to take part in the Thailand Working Dog Championship organised by the Royal Thai Army, which runs until Monday.
The princess was initially taken to Pak Chong Nana Hospital, where medics administered first aid under the advice of royal physicians. Once her condition had stabilised, she was airlifted to King Chulalongkorn Memorial Hospital in Bangkok.
The Department of Religious Affairs and monks at Wat Ratchapradit Sathit Maha Simaram in Bangkok held a chanting session yesterday to wish the princess a speedy recovery. Culture Minister Itthipol Kunplome also attended.
Mr Itthipol said Their Majesties the King and Queen gave saffron robes and other offerings to the monks as part of merit-making via their representatives.
The Secretariat of the Sangha Supreme Council has said all Buddhist temples in Thailand and others overseas would hold chanting sessions daily to extend their best wishes to the princess.
Chaiyapon Suk-iam, director-general of the Department of Religious Affairs, said other religious denominations, including Christians, Muslims, Brahmin-Hindus, and Sikhs, have been asked to perform religious rites to wish her well.
The Sheikhul Islam Office (Chularatchamontri) issued a statement instructing provincial Islamic committees and Muslims nationwide to hold daily prayers for the princess' speedy recovery.
The Catholic Bishops' Conference of Thailand has also asked all Christians in Thailand to include her in their daily prayers.
Meanwhile, cabinet ministers, MPs, government officials and members of the public turned up at the hospital's Bhumisiri Mangkhalanusorn Building yesterday to write get-well messages and present flowers.
Government spokesman Anucha Burapachaisri said Prime Minister Prayut Chan-o-cha and his wife Naraporn also went to the hospital to write similar messages, as did Deputy Prime Minister Prawit Wongsuwon, Pheu Thai leader Cholnan Srikaew, and Paetongtarn Shinawatra, head of the party's inclusion and innovation advisory panel.
The public can deliver their blessings online at wellwishes.royaloffice.th.