Chao Phraya translates to “the Chief”, such is the importance of this River to the Thai Nation.
It is along this river that international trade emerged between the river capital of Ayutthaya (and later Bangkok) and the great civilisations of Asia. From this maritime trade, the Kingdom on the Chief River became the most wealthy in the River basin. With his wealth, the Ayutthaya Kingdom was able to build canals to the neighbouring rivers, allowing to extend their irrigation systems, and also transport their influence to dominate other Kingdoms and Chiefdoms, eventually forming the great Kingdom that continues to thrive today.
You aren’t likely to see the Chao Phraya much, as when the train gets close enough, your views may be blocked by its natural levies or human development on its shoreline. But the Chao Phraya and the rivers that feed it will never be far on the Northern Line.