The Lanna language ภาษาล้านนา, commonly referred to as Kam Muang คำเมือง and sometimes called Thai Yuan, is still spoken by millions in northern Thailand (and thousands more in Laos) as the local dialect. Dating back to the pillars of the Lanna kingdom circa 13th century, throughout the centuries, the Lanna tongue has assimilated vocabulary from Thai, Burmese, Lao, and even Chinese languages to develop a truly unique, soft, and pleasant sound, clearly distinguishable from the region’s other dialects.
Though Lanna boasts its own script—which thrived throughout the rise and fall of the Lanna civilization—as a result of Siam’s final annexation of Lanna in the 1930s, the Lanna alphabet has become obsolete and replaced with the Thai script for everyday use and writing of both Thai and Lanna texts. Nonetheless, the Lanna script can still be found in old religious manuscripts, texts, and temple scriptures throughout northern Thailand. See this link for more information about Lanna language and alphabet: