9 dated entries naming King of Siam, drawn from 9 separate years between 1549 CE and 1925 CE. Nothing here is written by us: each line is the sentence a Wikipedia year article used, and the link beside it opens the exact revision.
1549January 19 – Maha Chakkraphat is crowned as the King of Siam after having been installed on the throne in 1548 by Maha Thammaracha of Burma.source
18th century
1733January 13 – Borommarachathirat V becomes King of Siam (now Thailand) upon the death of King Sanphet IX.source
1767December 28 – Phraya Taksin, a minor provincial official in Siam (now Thailand), crowns himself as King of Siam, establishing the Siamese Thonburi Kingdom, taking the regnal name of Borommaracha IV and begins a 14-year reign of liberation and conquest; historically, he is known as "Taksin the Great".source
1782April 7 – Taksin the Great, King of Siam (Thonburi Kingdom) (b. 1734)source
19th century
1809September 7 – Buddha Yodfa Chulaloke (Rama I), King of Siam, founder of the Chakri dynasty of Thailand (b. 1737)source
1824July 21 – Buddha Loetla Nabhalai (Rama II), King of Siam (Thailand) (b. 1767)source
1851April 2 – Nangklao (Rama III), King of Siam (Thailand) (b. 1788)source
20th century
1910October 23 – Vajiravudh (Rama VI) is crowned King of Siam, after the death of his father, King Chulalongkorn (Rama V).source
1925November 26 – Prajadhipok (Rama VII) is crowned as King of Siam.source