Kalasin (กาฬสินธุ์) is a town in the Isaan region of Thailand, population ~34,000 (2015).
Historical evidence points to the city having been established during the Rattanakosin period in 1793. Thao Somphamit and his troops escaped from the left bank of the Mekong River and settled on the banks of the Pao River, which was called "Ban Kaeng Samrong". Then, he sent tribute to King Rama I the Great who later promoted Ban Kaeng Samrong as a city and renamed it "Kalasin" or "Mueang Nam Dam" (a black water town), which later became an important city. "Kala" means "black", "sin" means "water", so Kalasin means "black water". The king also appointed Thao Somphamit as "Phraya Chaisunthon" who became the first ruler of Kalasin.