Agence France-Presse (via Google News) has more.
I knew the character and the concept of the movie so I decided that I might as well play the part myself," the 57-year-old said.
A drama based on a book she wrote, the film focuses on a woman who suffers the double trauma of losing her daughter in a car crash and then undergoing a transplant in which she receives the heart of her deceased daughter.
This experience transforms the main character, Pimdao, from a driven business woman into caring philanthropist who travels around Thailand's rural regions to help develop schools in a drive to improve education.
The princess lost a son, Poom Jensen, in the Indian Ocean tsunami in December 2004 and says she travels frequently to remote parts of the Thai hinterland to promote education. But she brushed aside comparisons with Pimdao.
Dressed in a short, silk dress and sporting spectacular diamond chandelier earrings and diamond bracelets, Princess Ubolratana looked every inch the Hollywood diva during her stop at the world's premier film showcase.
While she has also acted in a few television movies, the princess said she would wait to see if her film was a success before deciding whether to trying her hand again.
Where the Miracle Happens will open in Thailand cinemas on August 7.