Having reigned since 9 June 1946, he is the world's longest-serving current head of state and the longest-reigning monarch in Thai history.

Its king, Bhumibol Adulyadej, assumed the throne in June 1946 and is the world's longest-reigning monarch.

King Bhumibol, 72, is also the world's longest-reigning monarch.

King Bhumibol, who is 64 years old and the world's longest-reigning monarch, inherited the throne through a series of tragedies.

With a reign of more than 59 years, King Christian was the longest-reigning monarch of Denmark-Norway.

He is the longest-reigning monarch of Denmark with a reign of more than 59 years.

The longest-reigning monarch of all-time is a matter of some debate.

Sobhuza II, at that time the world's longest-reigning monarch, died in 1982.

King Bhumibol, the world's longest-reigning monarch make a rare public appearance on his 84th birthday.

Bhumibol is, as of 2012, the longest-reigning current monarch.