A bus is also another way to get around bus - and wow it was great - but I did have a Thai colleague with me who knew which bus I was supposed to be on.
So I had a look - and I decided that it was best to really prepare yourself with a map of all the routes... I found a list on Wikipedia.
Then I looked for a map of these routes and I found them here and there are a lot of routes. So I would not hop on and off the buses but take them from A to B. But wonderful to get to the Immigration Office from the Victory Monument. So a little bit of organisation and all will be well.
There are air-conditioned and non air-conditioned buses and the A/C is sometimes freezing and the non A/C is very hot - do not sit next to the window for the sun - but there is a breeze.
Unless you get the bus with no air-conditioned it is raining - that was not easy!!!
Not sure how the costing works BUT you must have change - more than 50 or 100 Baht is not something to do - loose change is great.
Transit Bangkok is a wonderful site to help you do this;
Bangkok Bus Rapid Transit System (BRT)
Sky Train (BTS)
Chayo Phraya Express (Boats)
With all this why are there so many taxis, motorbikes and Baht buses...