One-siao coin

The siao coin was a fractional-denomination coin used in the pre-decimal currency system of Siam. The siao represented a unit valued at 1⁄2 of a fuang or 1⁄32 of a baht, placing it among the smaller circulating denominations of the traditional baht-based system. Early siao coins were produced in the distinctive podduang form characteristic of Siamese coinage, while later issues transitioned to flat, struck metal coins during the 19th century monetary reforms. The siao coin remained in use until Thailand adopted the decimal baht–satang currency system in the early 20th century.
It is also called pai when it was a podduang.