Bhumibol Adulyadej became the ninth king of Thailand in 1946 after the mysterious death of his older brother, King Ananda Mahidol. As king, Bhumibol reigned for over 70 years, making him Thailand's longest-serving monarch. He was born in Cambridge, Massachusetts while his father was studying at Harvard University. Every year on Father's Day in Thailand, there are celebrations and activities to honor the king that include decorating buildings and homes with the national flag, holding charity events, and monks dedicating prayers to the king's philanthropic work.