Not the Brown Tree Frog

Polypedates megacephalus. Actually not a tree frog but part of the bush frog family, so should be "Hong Kong Whipping Frog" or "Spot Legged Tree Frog". Female spawns in spring and males clamber on her back in sometimes quite large numbers. This is the only frog in Hong Kong that lives on trees and bushes. A common frog that is thought to have good eyesight, this hardy and adaptable species has been found on many of Hong Kong’s smaller islands where there is barely enough water for breeding.