Central Siam, the heart of Thailand, is the vast alluvial plain of the Chao Phraya and may be described as 55,000 square miles of almost unbrokenly monotonous scenery. The level of the land is but little higher than that of the sea and, during the dry season, tidal influence is plainly evident as much as 50 miles from the river's mouth. Alluvial deposits, brought in the season of floods from the northern hills, are, however, raising this level at an astonishing rate; geological evidence shows that within comparatively recent times a great part of the plain was covered by the sea and even now the northern shores of the Gulf of Siam, at the mouth of the Chao Phraya, are advancing seaward at a rate of almost a foot a year. Its rich soil, its abundance of watercourses, both natural and artificial, and its comparatively dense population combine to make it one of the most eminently suitable areas of the world for the production of fine rice.
As Central Siam is the heart of the Kingdom, the royal city of Bangkok or Krungthep is the very core of that heart. Situated on the banks of the Chao Phraya, some 20 miles from its mouth, this metropolis, whose history goes back not earlier than the mid-eighteenth century A.D., is the center for scholarship and the arts, the filter through which pass all goods and ideas received by the interior from the outside world, and the nucleus of one of the most highly centralized of national governments. Its citizenry of some 800,000 represents no less than 5 percent of the total population of the country.
Eastern Thailand is a huge, shallow, elevated basin, tilted toward the east, so that while its western rim stands 1,000 feet above the sea, its eastern rim is formed by low hills. The plateau is watered by the system of the Me Nam Mun, a tributary of the Me Khong. A poverty-ridden country of unproductive soil and adverse climatic conditions, it supports indifferently well a comparatively limited population.
Peninsular Siam is the narrow, northern two-thirds of the Malay Peninsula, sharply divided longitudinally by a mountain chain which passes down its whole length. It is a country rich in forests, cattle, fisheries, mines, and agriculture, and possessed of great natural beauty in the countless islets off its shores, its beaches lined with palms and casuarinas, and the verdure of it mountain-backed landscapes. Most of the developed natural wealth of the Kingdom is found in this portion, which has fine systems of highways and railroads.