Chao (monarchy)
"Chao" (Thai: เจ้า) is a title of the ruling prince of Chiang Mai (also called Lannathai), and people who were related to the ruling prince of Chiang Mai. This system is called "Chao har kan" (เจ้าห้าขัน)
After the fall of the absolute monarchy, the Chao har kan system was abolished by the People's Party (Khana Ratsadon - คณะราษฎร).
In present days, all of the "Chao" family used "Na Chiang Mai" for their surname.
Read more about Chao (monarchy): Chao Uparaja, Chao Rajawong, Chao Burirat, Chao Rajabute