Phra Bat Somdet Phra Poramenthra Maha Mongkut Phra Chom Klao Chao Yu Hua , or Rama IV, known in English-speaking countries as King Mongkut (18 October 18041 October 1868), was the fourth monarch of Siam (Thailand) under the House of Chakri, ruling from 1851 to 1868.