Chao Phraya is a title in the Siamese political hierarchy which implies much power and the control of tens of thousands of men. For example, when Thong Duang became Chakri or something like a general in 1775, he also gained the title Chao Phraya, so he was known as Chao Phraya Chakri.
This use of the term is now archaic, but you will hear the term Chao Phraya in Thailand today because it is the name of the country's primary river. The river is often referred to as Mae Nam Chao Phraya in Thai; mae nam, literally "mother water", is the Thai word for river. Its name reflects water's importance as a life-giver in Thai culture as well as this particular river's importance as a central lifeline and symbol of the Thai nation.
The Chao Phraya is formed by the confluence of the Ping, Wang, Yom and Nan rivers at Nakhon Sawan in west central Thailand; from there, the river flows through Bangkok to the Gulf of Thailand. The Chao Phraya is navigable for its entire length and, with its tributaries, drains most of western Thailand. The Chao Phraya delta is the rice bowl of the kingdom; even in Ayuthayan times, the area was rich and fertile, and it remains the country’s main rice-producing region, in many areas supporting two rice crops per year.
The many tributaries of the Chao Phraya delta are connected by canals that serve for irrigation and transportation. In fact, Bangkok used to be known as "The Venice of the East" because of the many canals that laced the city. When Anna Leonowens was in Siam in the late 19th century, there was only one road in Bangkok, and it was very short; most people traveled in boats on the waterways. King Chulalongkorn later had the first long street built in the city; it is still known by its original name, New Road. Unfortunately, there is little evidence remaining in Bangkok today of the verdant area filled with busy water passages that once was. Most of the canals have been covered over to make roads, and those that remain are stagnant and fetid. However, they are less prone to traffic jams than the streets that have sprung up in abundance, and visitors to Bangkok who aren't too frightened of a few polluted splashes would do well to utilize the water taxis which have become popular in recent decades.
An amazing journey can be had by hiring a boat for a tour of the waterways, preferably going all the way to Ayuthaya. If you can ignore the whine of the boat's engine, you can almost think you have traveled back in time as you pass simple houses on stilts protruding out over the water, women kneeling on homemade docks washing clothes in the river, naked children leaping into the water with internationally-recognizable joy. Vendors still paddle these waterways as they have done for centuries, selling fresh fruit, noodle soup, and other tasty goodies. It is beautiful and peaceful, a perfect antidote to the filthy bustle and noise that is Bangkok.