Bangkok Skytrain

I think the fastest way to get around Bangkok is the BTS. Also the BTS is understood well by taxi drivers and bus attendants so can be easier to reach.

The cost varies on where you are going but the buying of tickets is pretty simple as long as you have change. If you do not have change there is usually a ticket counter where they will give you change but for some reason do not seem to sell tickets.

The cost of the BTS can be more than a metered Taxi if you have more than one person but the speed usually makes up for the cost. The only real down side is how crowded the BTS can get and you may have to thank the person behind you for pushing you all the way into the train.

There is now a 1 day pass for 120 baht (about 4 US dollars) that gives you unlimited travel on the BTS for the day. I have not bought one yet but seems like a good deal if you are going to take a number of trips in one day.