Princess Suddhadibya
Her Royal Highness Princess Suddhadibya Ratana, Princess of Sri Ratana Kosindra, was the 19th child of His Majesty King Chulalongkorn, and the eldest child of Her Majesty Queen Sukhumala Marasri.

From the picture, you can see that she was one of, if not the most beautiful princess of Siam.  She looked like a modern day lady in the clothes of royal past.  She showed grace in the photograph, a rare find in Thai women these days.

So far, I have not found much information on the princess, but to my knowledge, at one time she was a personal assistant to her father, King Chulalongkorn, acting as his personal secretary.  She was never married, and lived all her life in the Grand Palace until her death in 1923, at the older-than-average age of 46.

The Princess, standing next to her father, King Chulalongkorn, on a Royal Visit to Indonesia