Krom Phra Ratchawang Bowon Sathan Mongkhon กรมพระราชวังบวรสถานมงคล, colloquially known as the Front Palace (Thai: วังหน้า, RTGS: Wang Na), 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.

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" (Thai: กรมพระราชวังบวรสถานมงคล) (lit.

With the foundation of the Chakri dynasty in 1782, Phutthayotfa Chulalok made his younger brother Bunma the Front Palace (as Maha Sura Singhanat).

Ironically, with the exception of Prince Itsarasunthon (who succeeded to the throne as Phutthaloetla Naphalai), none of the Rattanakosin Front Palaces were actually crowned as they were mostly the monarch's siblings.

The Front Palaces during the Rattanakosin period wielded great power, with their own private army and even a navy.

[2] The conflicts between the reformist King Chulalongkorn and conservative Vice King came to a head in the so-called Front Palace Crisis in 1874—a fire in the Grand Palace was attributed to the Vice-King Wichaichan, who sought protection in the British consulate.