In the seventeenth century, Chan Buddhist masters from monasteries in South China boarded merchant ships to Chinese merchant colonies in East and Southeast Asian port cities to establish or maintain monasteries. Typically, Chinese seafarers and merchants sponsored their travel, and sovereigns and elites abroad offered their patronage. What were these monks and their patrons seeking? This study will investigate the question through the case of one Chan master, Shilian Dashan, who journeyed to the Vietnamese kingdom of Cochinchina (Dang Trong) in 1695 and 1696. In Dashan, we see a form of Buddhism thought to have vanished with the Silk Road: that is, Buddhism as a ‘missionary religion’ able to propagate branch temples through long-distance networks of merchant colonies, and to form monastic communities within the host societies that welcomed them. This evident agency of seafaring Chan monks in early modern times suggests that Buddhism’s role in commerce, diaspora, and state formation in early modern maritime Asia may compare to religions like Islam and Christianity, and deserves further study.