The article analyses the Russian Orthodox Church’s missionary activity of the in Southeast Asia, with a focus on its prerequisites and the stages of its development. ROC missionary work in the region could build on the experience of pre-revolutionary spiritual missions in Asia, as well as on the Orthodox communities of Russian emigrants after the revolution. Important factors are also the formation of the global labor market; international tourism; and the aspiration of compatriots living abroad to preserve the “Russian World” (Russkii Mir). The article analyses the Russian historiography of the missionary activity of the Russian Orthodox Church in Southeast Asia. With the establishment of the Patriarchal Exarchate in Southeast Asia in 2018, with its center in Singapore, a new stage of missionary activity in the region began. The establishment of the exarchate in Southeast Asia brought about the systematical management of the numerous Orthodox parishes that appeared at the turn of the millennium in this region. Relying on little-known and understudied historical sources, the authors identified the forms of missionary work in various countries and assessed the scale of activities in relation to the prevailing confessional traditions. This includes an analysis of missionary work in countries dominated by Buddhism (Thailand, Cambodia, Laos), Christianity (the Philippines), and Islam (Indonesia, Malaysia), with special attention paid to the situation in socialist Vietnam and multi-confessional Singapore. The authors conclude that the missionary activity of the Russian Orthodox Church in Southeast Asia has now passed through several stages from the emergence of the first Orthodox communities in the region to the formation of centralized structured management of the numerous new parishes, with missionary work conducted in ways that respond to the local characteristics.