I work nearby, its a combination of gentrification, Geylang is close to the City center & a lot of Mid Range (for Singapore) Condo's have been going up. Also, Prostitution is legal BUT under fairly strict rules, Street walkers are illegal but Knocking Shops as in the small streets of Geylang are legal & still there, not much of a GF experience. Plus they have installed a large network of CCTV in the area to minimize criminal behavior. I am sure that puts both Street Girls & Punters off.