Determine your budget before you shop--it will give you a good foundation for your shopping negotiations.
Explore the wholesale jewelry market on Mahesak Road just off Silom (similar to New York's West 47th Street). Here you'll find Thai, Chinese, Iranian, Israeli and Indian dealers who import and export cut stones.
Comparison shop at several stores before you buy, and never feel rushed in your decision. The educated buyer gets the best deals, especially in a place where negotiation is critical.
Pay a fair price by negotiating with the knowledge you've gained from comparison shopping. Nearly all jewelry shops negotiate, so always ask for a "special discount" on the quoted price.
Know what you're buying and purchase your sapphire with a credit card so that you can cancel payment if you've been defrauded. Gem receipts should always be marked "Subject to identification and appraisal by a registered gemologist."
Carry your sapphire home with you rather than having it shipped.
