Transport in Thailand is varied and chaotic, with no one dominant means of transport. Bus transport dominates in long distances and Bangkok, with motorbikes dominating in rural areas for short trips, supplanting bicycles. Road transportation is the primary form of freight transport across the country. Slow rail travel has long been a rural long-distance transport mechanism, though plans are underway to expand services with high-speed rail lines extending to several major regions of Thailand.
Domestic air transport, which until recently had been dominated by a select few air carriers, has recently seen a surge in popularity due in large part to the expanding services of low cost carriers. In Bangkok, Pattaya, and other large cities, public motorbike taxis take people door to door. An overwhelming number of taxis can also be found in Bangkok. Since the country's first rapid rail transit line opened in 1999 in Bangkok, daily ridership on Bangkok's various transit lines has risen to over 800,000, with multiple additional lines either under construction or being proposed.
Private automobiles, whose rapid growth contributed to Bangkok's notorious traffic congestion over the past two decades, have risen in popularity, especially among tourists, expats, the upper class, and the growing middle class. A motorway network across Thailand has been gradually implemented, with motorways completed in Bangkok and most of central Thailand. Areas with navigable waterways often have boats or boat service, and many innovative means of transport exist such as tuk-tuk, vanpool, songthaew, and even elephants in rural areas.
-: Railway :-
The State Railway of Thailand (SRT) operates 4,070 km of 1.000 m gauge railway line (372.63 km double track and 106.01 km triple track).
The SRT operates all of Thailand's national rail lines. Hua Lamphong or Krungthep Station is the main terminus of all routes and starts in Bangkok; Phahonyothin and ICD Ladkrabang are the main freight terminals.
The SRT has long been popularly perceived by the public as inefficient and resistant to change. Trains are usually late, and most of its equipment is old and poorly maintained. The worst financially performing state enterprise, the SRT consistently operates at a loss despite being endowed with large amounts of property and receiving large government budgets; it reported a preliminary loss of 7.58 billion baht in 2010. Recurring government attempts at restructuring and/or privatization throughout the 2000s have always been strongly opposed by the union and have not made any progress
-: Metro Systems :-
Bangkok Metro or MRT
Bangkok Skytrain or BTS
Pattaya Monorail (proposed)
Hat Yai Monorail (proposed)
-: Rail links to adjacent countries :-
Malaysia - same 1,000 mm (3 ft 3 3⁄8 in) gauge
Laos - 1,000 mm (3 ft 3 3⁄8 in) gauge across
Cambodia - disused (being rebuilt)
But a projected extension will rebuild the route.
-: Bus transport :-
Bus service Buses are a major method of transportation for people, freight, and small parcels, and are the most popular means of long distance travel. Tour and VIP class long-distance buses tend to be luxurious, while city- and other-class buses are often very colorful with paint schemes and advertising.
There are fundamentally two types of long-distance buses in Thailand:
those run by The Transport Company, Ltd., (TCL), the state-owned bus company. Known to Thais by the initials บขส (pronounced baw-kaw-saw), this 80-year-old company was formed by the government to ensure that citizens in even the most far-flung localities had access to the capital city, Bangkok. TCL buses are easily identified by the large golden coat of arms appliqued to each side of the bus.
those operated by private bus companies.
These are too numerous to list and offer hundreds of routes in various service categories (express, VIP, local, air conditioned, etc.)
Local buses and Bangkok city buses come in various sizes, types, and prices, from half size, full size, double length, open window, fan, and air conditioned.
Alternative transport Includes tuk-tuk, taxi, van (minibus), motorbike taxi, songthaew, boats (in canals and rivers).
-: Air transport :-
Major international airports
Don Mueang International Airport (DMK) (Old Bangkok Int'l)
Suvarnabhumi Airport (BKK) (New Bangkok Int'l)
-: River and canal transport :-
In Bangkok, the Chao Phraya River is a major transportation artery, with ferries, water taxis (the Chao Phraya Express) and long-tailed boats. There are local, semi express, and express lines for commuters, though the river winds a lot, which can make the trip much farther than by bus. There is also the Khlong Saen Saeb boat service, which provides fast, inexpensive transport in central Bangkok.
-: Ferries :-
Ferry service between hundreds of islands and the mainland is available, as well as across navigable rivers, such as Chao Phraya and Mae Khong (Mekong). There are a number of international ferries.
Source : http://en.wikipedia.org/wiki/Transport_in_Thailand