I think need to come really early, a Mandai photographer who happened to be around when I took this photo mentioned this kingfisher will fly away to the other side of the aviary after 9.30am (which I can confirm based on this single instance).
As @FoxBat mentioned, I spotted it near the flamingo pond.
I think other zoochatters used to spot it near the feeding station - the one that they cordoned off for 9.30am feeding session. @Leo K. uploaded a photo before and there was some discussion of where to spot it.
I've spotted it once in the late afternoon at the clearing where the Shoebill and Yellow-billed Storks often hang out. It was like striking the lottery!