The Dusit Zoo is not a bad place to visit and its very cheap to get in. Dreamworld is quite enjoyable too, and you can ride an elephant there as well. However the best day we had was at the Samphran Elephant ground, when you arrive the baby elephants are all out 'waiting' for you and you can interact, pat and feed them for as long as you want (I could have done this all day they were so cute), you can then go on a small 20 minute elephant trek, watch the crocodile show and then there is an elephant show where they re-enact some traditional battles etc and also play soccer. We had a great time here and arranged the tour through a booklet we found in our hotel. Lumpini park is quite nice too for a quiet break and you can ride the pedal boats on the lake.
Dusit Zoo Located near Vimanmek Palace in Central Bangkok, the zoo is open to the public every day
from 5:00 am to 6:00 pm. Tropical animals here include great grey kangaroos, Sumatra rhinoceros, Siamese crocodiles, guars and lesser mouse deer. A central pond features pedal boats.
Dusit Zoo with our 3 children (2yr twins + 6 month baby). It's not very easy to get to - in the end we caught the skytrain to Victory Monument and then got a taxi - but was a good way to pass an afternoon with the children. Lots of animals and they all seemed to be well cared for although the enclosures aren't very large. Only cost 30 baht entrance and the children were free. Only caveat is to avoid using the toilets if possible. They're the Thai 'hole in the ground' type and weren't very clean.