So with a day trip from Bangkok you can see the Tiger Temple near Kanchanarburi and also ride and feed an elephant before heading back late in the afternoon to Bangkok.
Many different companies offer similar tours so make sure you shop around to get the most out of your day. Depending on how much you want to fit in you can put anything from, just Elephant Tour, just Tiger Tour or even just a river rafting tour along some scenic route, or you can combine two or I think three different things.
The prices range anywhere from $50US to $150US depending on exactly how much you are doing, but remember these figures change a lot, have a look and get the best one for you at the time.
Re accommodation while you're in Bangkok, Batong Road has lots of cheap backpacker areas but once again, have a look around, you never know what you can find at short notice......