1 Salueng - Rama IV

Rama IV — Mongkut — came to the throne in 1851 after spending 27 years as a Buddhist monk, during which he taught himself Latin and studied Western astronomy well enough to accurately predict a solar eclipse in 1868. His reign saw Thailand's first machine-struck coinage, introduced partly to satisfy foreign merchants who distrusted the older bullet-shaped pod duang coins that had circulated for centuries. The Royal Mint in Bangkok received equipment from Britain, and production of flat, round coinage began in the late 1850s.

The salueng is one quarter of a baht — a subdivision rooted in traditional Thai weight standards that predated the coinage itself by generations.