Short answer — trusted options (by category):

• Official brand boutiques / luxury department stores in Malaysia (safest place for guaranteed authentic goods): Club21 (multi‑brand luxury boutique with Malaysian stores and e‑commerce), Isetan Kuala Lumpur (official department store online), SEIBU The Exchange TRX and Parkson. (club21.com)

• Large local/SEA marketplaces that sell new, branded luxury with authenticity policies: ZALORA (ZALORA Luxury — states “100% authentic” and has special luxury packaging/handling). (zalora-my.store)

• Global, reputable luxury e‑tailers that ship to Malaysia (authentic stock from brands/authorized boutiques): FARFETCH, NET‑A‑PORTER, MYTHERESA and MATCHESFASHION — all are well‑known authorized sellers of designer brands and offer international delivery. (farfetch.com)

• Specialist authenticated resale / consignment marketplaces (if you want pre‑owned luxury with authentication): Vestaire Collective, The RealReal, The Luxury Closet and Fashionphile — each publishes an authentication process / guarantees (though buyer vigilance is still wise). (faq.vestiairecollective.com)

• Platforms to be cautious about: Reebonz has been a major player in SEA resale but has had notable complaints and consumer‑protection cases; if you use it, check recent reviews and their authentication/returns policy first. (marketing-interactive.com)

Quick buying tips (to lower risk)

• Buy from brand‑owned pages or recognized authorized retailers; look for brand/retailer contact info and country‑specific sites. (club21.com)
• Prefer sellers that explicitly guarantee authenticity and offer a clear return/refund policy (ZALORA, Mytheresa, Vestiaire, The RealReal publish these). (zalora-my.store)
• Keep invoices, ask for proof of purchase/serial numbers (for bags/watches), and pay by card for buyer protection.
• For pre‑owned buys, use marketplaces that perform a physical authentication step (Vestiaire, The RealReal, Fashionphile, The Luxury Closet). (faq.vestiairecollective.com)

If you want, I can:

• give a short comparison table (fees, shipping to Malaysia, return period) for 4–6 of these sites, or
• check whether a specific store or listing is an authorized retailer for a particular brand — tell me the brand/store and I’ll look it up.