WeChat like other free Internet applications has users around the world without any specific marketing actions.
However, to expand the user base, Tencent decided to launch a local marketing plan one country after another starting from China and expanding gradually to other countries of Asia.
The strategy of expansion applied to India is quite successful. Facebook is currently growing fast its user base in India (similarly to Vietnam and Brazil).
Therefore, WeChat is competing against Facebook for user time. WeChat has a few advantages compared to the mobile application of Facebook. The war for the time of users is interesting.
The local teams of WeChat in Vietnam, Taiwan, Malaysia, Indonesia, Hong-Kong, Thailand, and Singapore are very active as well.