Last time I was there it was ok but was getting pretty rusty and some of the wood was rotting through, haven't been back since ... have they tidied it up?
I know of the playgrounds in Lumpini, Queen Sirikit and the Emporium but was hoping there might be some more that I haven't found yet!
I still haven't found anywhere better than the discovery museum playground which is like a mini adventure playground. They've just added a small new section as well, which has European quality equipment.
Everything is maintained well and as safe as a playground can be.