What is the most heavily populated plain in south asia?

The correct answer is the Gangetic plain

It is also known as the Indo-Gangetic Plain, Indus-Ganga Plain and the North Indian River Plain, and is found on the north of India and is an alluvial plain in its structure. Because of the rivers and the land around it, it is a home to many cities and places with high population with huge numbers of urban areas with highly dense population.