THE film crew tried to have her fall cushioned by a mattress. They also offered her a raincoat to help her brave the downpour.
But the princess would have none of such comforts during the shoot.
Princess Ubolratana Rajakanya Sirivadhana Phannavadi, eldest child of King Bhumibhol Adulyadej and Queen Sirikit of Thailand, was in Singapore this week for her first film, Where The Miracle Happens.
The movie is based on the princess' book, The Short Story Of Mine. She did double duty, acted and scripted. It opens in Thailand next month and here thereafter.
You can't be too certain with protocol in royal affairs - whether to sit one level below HRH, address on bended knee, walk backwards, speak obsequiously, and check on off-limit topics, if any.
The attendees at the media conference (for her film) also included a corp of diplomats from Asean and as far-flung as Peru and France, Thai professionals here, and guest-of-honour, Dr Vivian Balakrishnan.
So it was with some surprise that Princess Ubolrat (as she is addressed by her citizens) was forthcoming, more than we'd expected.
She strode into the ballroom of the Intercontinental Hotel in Middle Road, a flowing vision in heels and hairband and discreet diamonds.
She and her entourage are staying in the hotel, 'presidential suite', a hotel personnel told me, 'walk-in rate is $2,400, but of course, she is a guest of Government'.
After a string of formal words from the welcome committee, the royal 57-year-old mother of three greeted audience with 'Hi' and invited questions on the movie.
Miracle is the story of an ambitious businesswoman who loses her daughter in an accident, renounces her materialism and atones for her past fighting poverty.
The princess, who was born in Switzerland, was both reticent and open, whether to give too much or otherwise.
On her crying scenes, she said it was a challenge to show emotion. 'My tears don't come easy, I suppress them, as you know I lost my son.'
Her only son, Khun Poom Jensen, then 21, died in the 2004 tsunami.
Of the many village children featured in Miracle, and how they interacted, she said they made an impression.
'It's not hard to reach out to kids, they are very natural. At first, they may be uneasy.'
Here, Princess Ubolrat broke into a little laugh, 'but I'm not officially part of the royal family, so I'm not like the other members.'
She graduated from MIT (in Maths) and UCLA (in public health), and gave up her royal titles when she married a commoner, the American Peter Ladd Jensen. They are divorced.
She lived in the US until 2001 and now serves as a semi-official 'public relations princess' in Thailand. She does charity work for underprivileged children, her pet project.
As for the character, Pimdoa, that she plays (co-starring role), 'I hope I'm not as mean! I'm a gentle mother (she has two grown daughters) even though I drew a lot from my experiences.'
She is not new to being before the cameras, and hosts a travel series on Thai TV, 'Princess Diary', of course.
Her visit here contributed Singapore footage to the programme.
The rather sporty princess - an accomplished sailor - refused stunt doubles and naturally sent film crew into angst-overdrive when she did the burning schoolhouse scene herself.
'I like to give it my all,' she concluded.