First of all, the main climate type in Vietnam is tropical monsoon climate rather than subtropical monsoon climate.

Secondly, regarding the distribution of a large number of tropical rainforests in Vietnam: Tropical rainforest is a landscape type in a rainy climate. Vietnam is located on the windward slope of the northeast trade wind belt. Affected by the terrain, the chance of precipitation Much larger than other places, it is deeply influenced by the East Asian monsoon climate. The summer monsoon from the ocean brings it abundant precipitation. In addition, its tropical environment is very suitable for the growth of tropical plants. Therefore, it has a large number of tropical rainforests. Compared with the rainforests in the equatorial zone, this kind of rainforest has a more obvious leaf drying period. The seasonal change (seasonal change) is what makes it different from the tropical rainforest climate. The strict name of this kind of rainforest is Tropical monsoon forest.