I took my niece there early this year, take lot of her photo with animal. This is only one photo I have without people in the scene.
Quite a good zoo. Children will probably love it as it has the usual guests: tigers, giraffes,hippos and the rest. The elephants were as you can imagine quite popular.
There is as well a lake where you can rent one of those waterboats with pedals and pedal for half an hour ( 50 baths the 1/2 hour) and see the gardens. In the lake there are fish, alligators and turtles. Careful not to run them over ;-)
The access to the zoo is really cheap, 30 baths per person and as I said children will love it and it won't break the bank. The grounds used to be originally the private botanical gardens of king Rama V and you can see still the different species of flora cultivated here.
More info is here