Ooh...I 4got to ask u when exactly were u going to be in Singapore. because from Sept 28 onwards, they are having the F1 Grand Prix Night race, so starting from mid Sept onwards, hotel prices are going to be hitting sky high(heard it was ard 30% extra tax) and most places have already been fully booked.
As for attractions, the Zoo is pretty good and the Night Safari is the only kind in this world.
Shopping: Orchard Rd! So many different malls there, just go into every single one.
Designer shopping wise; don't bother with Chanel(unless its accesories, then yes its cheaper), Hermes and Balenciaga are also a little more expensive in Singapore.
U could get pretty decent prices on watches over there(Omega, Rolex, etc). Jewellery is also at a good price(24k gold though)
As for snorkelling, u can try to go to Phuket, Kho Samui or Krabi either from Bangkok or Singapore.
Food: definitely have to go to Newton Circus, Chomp Chomp and Lau Pa Sat.
Hotels: Ritz-Carlton, Fullerton, Raffles, Goodwood park.
any qns just ask me!!! more than happy to help!