The Chakri dynasty have ruled Thailand since king Taksin was declared mad in 1782. The name Chakri (Thai จักรี) derives from the title Phya Chakri, given to Rama I while he was a general in Taksin's army.
Until 1885 every king had a vice-king (Maha Uparaja, also often translated as second king), usually the brother of the king and the designated heir to the throne - however Rama II was the only former vice-king who actually ascended to the throne. When the vice-king died before the king, the title often remained vacant for several years. The system was abolished by King Chulalongkorn when his vice-king Bovorn Vichaicharn died. He then declared his oldest son the crown prince, but not vice-king.
