Yonok Nakhon Chaiburi Ratchathani Si Chang Saen (Northern Thai: ᩰᨿᨶᩫ᩠ᨠᨶᨣᩬᩁᨩᩱ᩠ᨿᨷᩩᩁᩦᩁᩣ᩠ᨩᨵᩣᨶᩦᩆᩕᩦᨩ᩶ᩣ᩠ᨦᩯᩈ᩠᩵ᨶ; Thai: โยนกนครไชยบุรีราชธานีศรีช้างแส่น) was a Tai semi-legendary kingdom based along the Kok River in the Chiang Rai Basin in northern Thailand, existed from 691 BCE to 638 CE. It was centered in Yonok Nahaphan (Chiang Saen District, Chiang Rai) and then moved to Wiang Prueksa (Fang District) after the old capital was submerged below Chiang Saen Lake due to an earthquake in 545.
Singhanati evolved into the Ngoenyang Kingdom in 638, which continued to the formation of Lan Na in 1292.