Lao, sometimes referred to as Laotian, is a Southwestern Tai language and the official language of Laos. It is also spoken in the Isan region of northeastern Thailand, where it is usually called the Isan language. The political split of the Lao-speaking population along the Mekong River resulted from the Franco-Siamese crisis of 1893. Lao is written in the Lao script, an abugida that evolved from early Tai scripts.