Overview
Krom Phra Ratchawang Bowon Sathan Mongkhon , colloquially known as the Front Palace, was the title of the uparaja of Siam, variously translated as "viceroy", "vice king" or "Lord/Prince of the Front Palace", as the titleholder resided in the physical residence of the same name. The office of Front Palace was considered second only to the king and regarded as the heir presumptive. The name, with its dual meaning, originated in the Ayutthaya period, and the holder later gained significant powers during the Rattanakosin period. Front Palace occupants were usually a son or brother of the reigning monarch. The office existed until the death of the last occupant, Prince Vichaichan, in 1885. King Chulalongkorn then abolished the office of an heir presumptive, introducing in its stead the Western concept of a crown prince as heir apparent, and styled the new office "Crown Prince of Siam".
Ayutthaya period
The Uparaja or Uparat concept of a Viceroy was of Greater Indian origin. In 1448, Sukhothai King Trailokanat was crowned as the king of Ayutthaya, uniting the two kingdoms. During the 15th century, the Kingdom of Sukhothai, which centered on Pitsanulok, served as the seat of most of Uparats, as they were, with few exceptions, also king of Sukhothai. After the first fall of Ayutthaya in 1569, Maha Thammaracha crowned his son Naresuan as Uparat and king of Sukhothai/Pitsanulok. Naresuan then had a palace built in front of his Royal Palace, to be his son's place of residence when visiting Ayutthaya—thereby giving rise to the name "Front Palace." In 1583, Naresuan annexed the Sukhothai kingdom to Ayutthaya, and Pitsanulok ceased to be the seat of the Uparat. After his coronation, Naresuan appointed his brother Ekathotsarot to be the Uparat, stating that his brother in the Front Palace had equal status to the King in the Royal Palace.
Phetracha in 1688 appointed his son Luang Sorasak (later Sanpet VIII) as the Uparat living at the Front Palace. For the first time the descriptive term used was "Krom Phrarajawang Bovorn Sathan Mongkol" ( (lit. The Great Auspicious Place). The Uparat was usually the brother of the king, and only heir presumptive to the throne, not heir apparent. This created an air of uncertainty about the succession upon the death of the king; keeping the heir close at hand in the Great Auspicious Place proved a means for keeping an eye on him, lest he presume too much.
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