Chulalongkorn’s first wife, Queen Sunanda Kumariratana, died at the age of 20 with her daughter during a shipwreck on May 31, 1880. Until then no one could touch the royal family, so they could not be rescued. You can see a memorial that was built in their honour inside the palace.
In 1932 the absolute monarchy of Siam was transformed into a constitutional monarchy by a bloodless coup. It is also true that since then the military has remarkable power in the country.
By the way, the story told by Anna Leonowens has no historical references, so it was the result of her imagination and a bit of plagiarism, with a commercial purpose.
Although she was actually in court for five years, she barely projected her influence on the royal family. In fact, she only shows up in an appendix to a shopping list, as a written reference.