Frogs have become extremely rare in Singapore now. I haven't seen any in years, not counting those imported American Bullfrogs served at restaurants and foodcourts. Last year I saw a couple of these "foreign" frogs huddled beneath some foliage at a pond in Botanical Gardens, they must have escaped from some kitchen somewhere close by (suspect a restaurant from Dempsey Road), but they aren't a local species.
Cheers!