King Rama IV, also known as King Mongkut, ruled Thailand from 1851 to 1868. He was a significant figure in modernizing the country, introducing reforms in education, government, and infrastructure. His reign is often noted for opening Thailand to Western influences while maintaining its sovereignty. Rama IV was also a scholar and a monk, having spent years studying in a monastery before ascending the throne. He is famous for his efforts in promoting science and technology, including the establishment of the Royal Astronomical Society of Thailand. His legacy continues to influence Thai culture and governance today.