Why did Hmong and Mien speakers migrate from China to Southeast Asia during the 19th century?

During the 19th and early 20th centuries, waves of Hmong and Mien speakers migrated from China to Southeast Asia primarily due to intense pressure from the expanding Han Chinese population.1

This migration was part of a broader historical trend during the Qing dynasty, which actively encouraged the movement of Han settlers into regions traditionally dominated by Indigenous or non-Han ethnic groups. This state-sponsored expansion into the southwest, combined with the resulting ethnic conflict and the displacement of local populations, created significant instability for minority groups like the Hmong and Mien. Consequently, many sought refuge by moving beyond China's borders into neighboring territories.231