Thai royalty, the fourth monarch of Siam (1851-1868), best known outside Thailand as the king in the 1951 musical and 1956 film The King and I, based on the 1946 film Anna and the King of Siam—in turn based on a 1944 novel by an American missionary about Anna Leonowens’ years at his court, from 1862 to 1867.
He was the oldest legitimate son of King Rama II, trained from childhood to assume the throne. Though he had slaves to answer every need, Mongkut’s life was filled with study and ritual. At 18, he spent a year in a Buddhist monastery and while there, his father died and his older half-brother, the son of a concubine, took the throne for himself as King Rama III. Mongkut had no taste to embark on a war and he lived as a celibate monk in the monastery for 27 years. He meditated and studied religion, Latin, English and astronomy and each morning, took his begging bowl to the street for his food.
When Rama III died in 1851, Mongkut assumed the throne as King Rama IV on 15 May 1851.
Small in stature, he was known for being wise, progressive, unpretentious, devout and just. He was the first Siamese ruler to recognize the vital importance of opening his country to the West at the same time as maintaining defenses against invasion. He reached shrewd trade agreements, opening foreign markets while avoiding external colonization. He was also the first Thai king whose face was seen in public.
He was also an astrologer. He wrote an astrological textbook called “Shards of King Mongkut” and he has been regarded and honoured as the “Father of Thai Astrology.”
Mongkut was glamorized in the 1946 film “Anna and the King of Siam.” He had ruled for 10 years and was 55 years old when Anna Leonowens arrived in Siam as a tutor. At that time he had hundreds of wives and 67 children and during the next five years he would father another 18. He joked that had to make up for nearly three decades of celibacy, However, his many wives were allowed to “withdraw” from the palace, if they chose, to marry others.
In 1867, Anna left Siam, a sad and affectionate farewell. Though her imperialistic ways had often been abrasive, she was loved by the wives and children for her kindness. The following year, Mongkut took a large entourage to a swampy area to see an eclipse that he had predicted from his enduring love of astronomy. The mosquitos in the area gave malaria to the entire party; many survived but not King Rama IV. Having been born on the morning of a Full Moon, he died on the evening of a Full Moon, at 9:05 PM on 1 October 1868 at age 63, surrounded by chanting monks in the Grand Palace in Bangkok, leaving the throne to his oldest son, Chulalonghorn.
Link to Wikipedia biography