Thailand's transportation system is not fully developed, but it is growing rapidly. Owned and operated by the government, the railways, consisting in 2002 of 4,071 km (2,530 mi) of track, radiate from Bangkok to Malaysia in the south, to the Cambodian border in the east, to Ubon Ratchathani and Nong Khai in the northeast, and to Chiang Mai in the north.
The highway system, significantly expanded during the 1960s and 1970s, serves many areas inaccessible to railway. In 2001 there were 64,600 km (40,142 mi) of roadway, including 62,985 km (39,139 mi) of paved road. Modern two-lane highways now connect Bangkok with the rest of the country. In 2000, registered motor vehicles totaled 4,667,700, including 1,529,000 passenger cars.
Waterways, both river and canal, are Thailand's most important means of inland transport; they carry much of the nation's bulk freight over a network of some 4,000 km (2,500 mi). The Chao Phraya River with its tributaries is the main traffic artery, and Bangkok is its focal point. The modern port of Bangkok at Klong Toey is the chief port for international shipping. Lying some 40 km (25 mi) inland from the sea, its harbor is navigable for vessels up to 10,000 tons, but constant dredging of the Chao Phraya is necessary. To relieve the congestion at Klong Toey, a new modern port was being developed at Sattahip, a former US naval base, and new seaports at Laem Chabang and Hap Ta Phut. Phuket Harbor in southern Thailand has been improved to accommodate 15,000-ton cargo ships. An extensive shipping service also exists along the Gulf of Thailand, and a small Thai merchant fleet plies between local and neighboring ports. In 2002, there were 297 oceangoing vessels of more than 1,000 gross tons in the Thai merchant fleet (up from only 80 in 1986), totaling 1,616,314 GRT.
Since the end of World War II, Bangkok has become an important center of international aviation. In 2001 there were 110 airports, of which 62 had paved runways. Principal airports include Bangkok International at Bangkok, Chiang Mai, Hat Yai at Haadyai, and Phuket International at Phuket. The government-owned Thai Airways International and Thai Airways Co. handle international and domestic air traffic, respectively. In 2001, scheduled airline traffic carried 17,392,100 passengers and 1,699 million ton-km (1,055 million ton-mi) of freight.