Sam-ông (三王, Thài-kok-gí: กรมพระราชวังบวรสถานพิมุข) ia̍h sī hoan-e̍k chò tē-sam-ông (第三王), sī Siam-lô uparaja ê thui-tēng kè-sêng-jîn (heir presumptive) ê hâm-thâu.

Koh khoàⁿ siu-kái