Funny, my last few visits to lumpini I have hardly seen any lizards - I always go to try and see them.
Fun fact: my username is because of them! On my first visit there my friend and I were observing a lizard near a bridge and an older European guy saw us pointed at it then to the distance saying in broken english, excitedly, "many! many! many!". My friend and I find things like this quite funny lol.
Saw one of those snake catcher programmes on Nat Geo TV once and they were in Bangkok, not long after the 2011 floods I think. They were called to lumpini park to catch a massive python hiding in a tree. Would love to see a python in the park! I guess it was probably planted for dramatic effect though.