This article examines the activities of Chinese “secret societies,” which were often called tua hia and angyi, in Siam and the Siamese authorities’ reactions to them from the late nineteenth to early twentieth centuries. Thai archival records reveal that incidents of revolt by the Chinese started to appear in the mid-nineteenth century, and became more frequent and widespread toward the end of the nineteenth century. After the large scale clash among angyi in Bangkok in 1889, the government started to adopt more strict administrative measures to control them, which culminated in the Secret Society Act of 1897. However, the government’s efforts to control their activities proved ineffective. Many of the members were foreign subjects and Western powers did not consider that forming such societies would be a criminal act to be punished or prohibited. Sensitivity of the issue of foreign subjects is also reflected in historiography, such as Prince Damrong’s writings, which have downplayed foreign factors.