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 Buses
Bangkok Bus Rapid Transit System (BRT)
Sky Train (BTS)
Chayo Phraya Express (Boats)
Khlong Boats
MRT
With all this why are there so many taxis, motorbikes and Baht buses...