The Motorcycle Taxi
Not for the feint hearted - the Motorcycle Taxi is fast, cheap, convenient, exhilarating, and often, a bit dangerous! Get on the wrong one and you can be in for a white knuckle ride! You'll recognise a Motorcycle Taxi by the fact the rider is wearing a vest of some description (blue, orange, any number of colors) with a number on the back over his shirt. The cost of the trip is entirely dependent on where you are going and sometimes how much you weigh! You should wear a helmet or the rider can be fined.
The Bus System
The bus system in Thailand is well organized, cheap and efficient. In cities a bus ticket costs around 3.50 Baht for a standard bus without air-conditioning on a journey of up to 8 kilometers. This is amazingly cheap if you think about it, but they do pack them in, Air-conditioned buses on inner-city bus routes cost up to 20 Baht per trip depending on the destination and type of bus, smaller air-conditioned buses being the most expensive. These prices are likely to go up soon as the price of oil goes up worldwide. However, comparing costs of public transport in places like London, you really are onto a winner!
The Tuk-Tuk
Thailand's ubiquitous form of transport. the Tuk-Tuk is the all purpose, all terrain vehicle of Southeast Asia. the Tuk-Tuk is not cheaper than a taxi, especially on shorter journeys. However, if you are coming to Thailand, and you don't have at least one Tuk-Tuk journey, you are missing out!
Long-tail speedboats
Long-tail speedboats are motorcycle taxis on water; sometimes a bit messy, they occasionally feel a bit dangerous, but above all, fast! Whether you want to cross the river or get to an island, these guys will be ready to give you a pretty exhilarating trip!
Transport specific to certain areas
The Bicycle Rickshaw
Yes, they still exist in Thailand. The Bicycle Rickshaw is still prevalent in the certain provinces. Costs vary being a bit less than as motorcycle taxis, but obviously a lot slower. You might end up paying out a lot in tips - they work so hard! Have mercy; the average Samlaew driver is half the size of the average European or North American!
The 'Baht Bus'
The Baht Bus no longer costs 1 Baht; expect charges of between 5 Baht and 20 Baht depending on where you are and what you are doing. The Baht Bus is particularly associated with Pattaya where all major attractions are in a limited area and Baht Buses simply circle the area and pick people up.
The 'Ferry Boat'
Like most cities with rivers in Thailand, Bangkok's has regular ferries taking people from one side of its main artery, the Chao Praya River, to the other. Of course in the south, where there's extensive travel between the mainland and Thailand's islands, ferries are bigger affairs, carrying passengers and cars.
Costs certainly vary - a trip across a river could be as low a cost as 1 or 2 Baht
The 'Express Boat'
Express boats run down rivers stopping at each quay and picking up passengers. With fares of only 4-10 Baht, if they are heading in your direction, they are the quickest way of getting anywhere, especially in Bangkok.