In respect of the Mon homeland, A.H. Chiristie once suggested Tongkin Basin as the swarming ground of the Mon-Khmer. It is no doubt cognate to the Mon-Khmer word for river. The authors stated that ancient South China was almost exclusively populated by non-Chinese people. All the statements support the assumption of taking Yangtze Kiang Valley as the original homeland of the Mon-Khmer. Because the Mons had obtained the Sanskrit word Mahasamudra for sea or ocean their own word for ocean labi subsequently changed to river and their word for river, to creek or stream.
Irrigated rice is one of the great economic discoveries in the history of humanity.
It is the prime product of Southeast Asia and the first contribution to civilization. Due to the rapid growth of population the Tongking Plain became overcrowded and a great number of Mon-Khmer fell back along the Red River, the shortest and easiest route to the Ganges Plain in India. On their way they passed the delta of the Ayeyarwady River in Ramannadesa in Lower Myanmar. In 832 Nancho sacked the PYU capital, and in 835 the two chief cities, very likely Mon, of Lower Myanmar. They formed part of a new migration of Tibeto-Myanmar speaking people.