Recently, Southeast Asian people, its food, natural sceneries and so on have been increasingly exposed to Korean people through mass media and multi-cultural events. At the same time, Koreans can frequently encounter Southeast Asians in their everyday lives. Thus, specific images and discourses of Southeast Asia has been established in our society, which creates a new social trend called ``Southeast Asia phenomena``. In short, ``Southeast Asia phenomena`` means a totality of Korean people`s experience of Southeast Asian and their perception on the region. On the one hand, ``Southeast Asia phenomena`` is a result of inflow of Southeast Asians and their culture into Korea. On the other hand, it is also a consequence of Korean people`s understanding of Southeast Asia from their trip to Southeast Asia or from their interactions with Southeast Asian people. This article aims to analyze the origin and diffusion of ``Southeast Asian Phenomena`` in Korea in the context of Southeast Asia focusing on 4 topics, that is, migrant workers, overseas investments, retirement migration, study-abroad categorized as human movement. This article is also about a country-by-country comparative analysis both at the macro level and the micro level. At the macro level, overseas investments and trade, human exchanges, positive perception to Koreans which considered to be the structural causes become a strong mechanism playing a important bridge role between Korea and Southeast Asia. So these create the high probability of the emergence of ``Southeast Asian Phenomena`` At the micro level which is more direct causes of ``Southeast Asian Phenomena``, the economic cause is the most important common cause for 4 Southeast Asian Phenomena. Additionally, Korean wave is also remarkable common cause creating ``Southeast Asian Phenomena`` even it is not the origin in the context of Southeast Asia. The diffusion of ``Southeast Asian Phenomena`` is different by the topics and the elements contributing to create the favorable situation for the diffusion are not only overseas investments and trade, human exchanges at the macro level but also policy elements at the micro level. The relative differences of the causes of ``Southeast Asian Phenomena`` in the country-by-country analysis are found. Regarding overseas investments in Vietnam and Cambodia, the economic degree of freedom in Cambodia is higher than in Vietnam. Even Korean Wave has had the longer history in Vietnam, but the favorable perspectives on Korean Wave are stronger in Cambodia. For migrant workers from Vietnam and Indonesia, the economic causes in Vietnam are more significant than in Indonesia. The impact of Korean Wave is stronger in Vietnam than in Indonesia. In case of study-abroad, the social-cultural elements and policy elements are more diverse in Malaysia than in Korea. For the Korean retirees who immigrate to the Philippines and Malaysia, the economic causes in the Philippines is more significant in Malaysia.