SIAM (MUANG THAI, THAILAND), an independent kingdom, in the Indo-Chinese or Further India Peninsula, with an area of about 220,000 sq.m.
The country contains four natural regions: (I) Nora. About 6o,000 sq.m. in area, a series of parallel ranges, lying north and south, and rising from mere gently sloping acclivities in the south, to precipitous masses in the north. Between these ranges of limestone and red sandstone flow four streams, turbulent and shallow in their upper reaches, but slow moving and deep where they near the points of junction. Of these the Menam is the largest, deepest and most sluggish. The districts watered by the lower reaches of the four rivers are fertile and contain a considerable population of Siamese. Farther north live the Laos, scattered in villages along all the river banks, and numerous communities of Shan, Karen, Kamoo and other tribes in the uplands and on the hill tops.
(2) East. About 70,00o sq.m. practically a huge basin, the bottom of which is a plain lying from 200 to 30o feet above sea level, and the sides hill ranges rising to between 1,00o and 2,000 feet. The plain is mostly sandy and almost barren, subject to heavy floods in the rainy season and to severe drought in the dry.
The hills, composed of limestone, red sandstone, etc., are clothed with a thin shadeless growth of stunted forest which only here and there assumes the characteristics of ordinary jungle. Nearly 2,000,00o people, mixed Siamese, Lao, and Cambodian, probably amongst the poorest peasantry in the world, occupy this inhos pitable region.
(3) Central. Estimated area, 50,00o sq.m. This is the heart of the kingdom, the home of the greater part of its population and the source of nine-tenths of its wealth. It is a great alluvial plain flanked by high mountains on the west, inclining gently to the sea in the south and round the inner Gulf of Siam and with a long strip of mountainous seaboard stretching out to the south east. The western range, whose highest peak is Mogadok (5,000 ft.) forms the boundary between central Siam and Burma. The eastern and south-eastern ranges also have peaks of from 3,00o to 5,000 feet. The rivers, with the exception of the Menam Chao Phaya, the principal river of Siam, are short and of little value except for traffic by small native boats. The Menam Chao Phaya
flows from the point where it is formed by the junction of the rivers of northern Siam almost due south for 154 m., when it empties itself into the inner gulf. In the neighbourhood of Chainat, 40 m. below Paknam Poh, it throws off three branches, Menam Noi and the Lopburi, which rejoin the parent stream much lower down, and the Suphan which has its own outlet to the sea. About the centre of its course, the main river is joined by its only tributary, the Nam Sak, which drains the most easterly part (the Pechabun valley) of north-east Siam. The Menam Chao Phaya is a deep, fairly rapid river, subject to a regular rise and flood every autumn and is affected by the tide 5o m. inland. It is navigable for 20 m. by vessels of over 1,500 tons and, if it were not for the enormous sand bar at the mouth, ships of almost any size could reach Bangkok. (See BANGKOK.) Vessels up to 300 tons and 12 ft. draught can ascend the river 5o m. and more, and beyond that point large river boats and deep-draught launches can navigate for many miles. The river is loaded with silt which, during the flood season, is deposited on the plain. With the exception of the forest growth on the slopes of the bounding hills the whole of central Siam is open rice-land, alternating with great stretches of grass, reed jungle and bamboo scrub, much of which is under water for quite 3 months each year.
(4) Southern. Area about 20,000 sq.m. This comprises that part of the Malay Peninsula belonging to Siam. It is a narrow strip at the north but widens out to the south where the habitable section consists of the lower slopes of the range with the valleys and small alluvial plains which lie between its spurs. The remainder is mostly covered with dense forest containing several kinds of valuable timber. The coast, both east and west, is much indented and studded with islands. The rivers are small and shallow. The highest mountain is Kao Luang, an almost isolated projection over 5,000 feet high, round the base of which lie the most fertile lands of this section, and near which are situated a few small towns, such as Bandon, and many villages.