according to yahoo answer, the best money changers in singapore are located in "the arcade" at raffles place.
verified -> changing 1000 yen just need sgd 12.77 at "the arcade" vs sgd 13 at other places :)
l.i.g.h.t:s.h.a.d.o.w:p.h.o.t.o.g.r.a.p.h.y