Short answer — the places locals and visitors go for luxury fashion in Singapore:

• Orchard Road (ION Orchard, Paragon, Ngee Ann City / Takashimaya, Mandarin Gallery, Scotts Square): Singapore’s main luxury shopping strip with most flagship designer stores and large department stores. (visitsingapore.com)

• Marina Bay Sands — The Shoppes: the island’s other top luxury destination (many duplex flagships, jewelry/watch boutiques, and concierge/personal-shopping services). (marinabaysands.com)

• DFS / T Galleria (Scotts Road): the big duty‑free multi‑brand luxury store popular with tourists for watches, bags and cosmetics. (trbusiness.com)

• Raffles Arcade / Raffles City area: historic Raffles Arcade plus nearby Raffles City and Capitol malls carry curated luxury and boutique watch/jewellery stores. (rafflesarcade.com.sg)

• Boutique / local‑designer areas (Haji Lane, Tiong Bahru, Dempsey Hill, Design Orchard): for independent labels, limited‑edition pieces and designer boutiques (not mass luxury flagships). (kamponggelam.com.sg)

Quick practical tips:

• Most malls are open ~10:00–22:00; Orchard and Marina Bay Sands concentrate the widest selection of designer flagships. (visitsingapore.com)
• Tourists can claim GST refunds on qualifying purchases via the eTRS system at Changi / Seletar airports — present your passport and receipts. (customs.gov.sg)

If you want, I can tailor suggestions by brand (where to find Gucci / Louis Vuitton / Chanel), by neighborhood to match your hotel, or by whether you prefer flagship stores vs. independent designers.