Bangkok and coloured stones: the real trade, and the scam.

What Bangkok actually is in this trade

Thailand's position in coloured stones is not a tourist story. For decades Bangkok has been a principal global centre for the cutting, heat treatment and wholesale trading of ruby and sapphire, and a significant share of the corundum that reaches the great jewellery houses of Europe and the auction rooms passes through Thai hands somewhere between the mine and the setting. Thai cutters are among the most skilled in the world, the heat treatment expertise developed here is a specialism other centres still send stones to acquire, and the wholesale market has the depth that only comes from being where the trade lives.

That trade is concentrated in the Silom area, where the Jewelry Trade Center building and the surrounding streets hold hundreds of dealers, laboratories and cutting operations, and in Chanthaburi, a town three to four hours east of Bangkok where the weekend gem market on and around Si Chan Road remains the country's live trading floor. Neither is a shopping destination in the retail sense. Both are places of business, where the customers are dealers, and where an unaccompanied private buyer without technical knowledge is not the intended audience. This is important to understand before you go looking.

What is worth buying here

Ruby and sapphire are the honest answer, with the caveat that the historic Thai and Burmese sources are largely worked out and most material now arriving in Bangkok comes from Mozambique, Madagascar, Sri Lanka and elsewhere for cutting and treatment. Blue sapphire in particular offers real value here relative to Gulf retail, and the range of sizes and qualities available in one afternoon exceeds what a private buyer will see anywhere in the region. Spinel, zircon, tourmaline, garnet and other less famous species are also plentiful and comparatively inexpensive.

Diamonds are a different matter. Thailand is a jewellery manufacturing centre rather than a diamond trading centre, and a Gulf buyer will find better selection and pricing in Dubai, Antwerp or Mumbai. Pearls are not a Thai strength. And emerald, while traded here, is not where Bangkok's expertise sits. Be sceptical of any Bangkok shop presenting itself as a diamond specialist to a visiting foreigner; the trade's own diamond buying does not happen in retail units in tourist districts.

Certification is the whole subject

Almost everything that can go wrong in a coloured stone purchase is a question of identity, origin or treatment: whether the stone is natural or synthetic, whether it is the species claimed, whether it has been heated, filled, diffused or dyed, and where it came from. None of these can be established reliably by eye, by a shop's assurance or by a certificate printed on the premises. They are laboratory questions, and the answer costs a fraction of the stone's value.

Three names matter. The Gemological Institute of America maintains a laboratory in Bangkok and its reports are the international reference standard. The Asian Institute of Gemological Sciences, founded in Bangkok, is a long established regional laboratory and school whose reports are widely accepted in the trade. And the Gem and Jewelry Institute of Thailand, a public organisation under the Ministry of Commerce, issues reports and also runs a shop certification programme intended to identify retailers that meet its standards. A report from one of these, issued to the specific stone and matching it by measurement and photograph, is what you are buying alongside the stone itself.

• Insist the stone is sent to an independent laboratory before the balance of payment, not after.
• Check that the report's measurements, weight and photograph match the stone in front of you.
• Read the treatment line specifically; heated is normal and disclosed, diffused or filled is a different price entirely.
• Treat an in house certificate from the selling shop as marketing, not evidence.
• For a significant purchase, engage an independent gemmologist to attend with you; the fee is trivial against the risk.

The tuk tuk gem scam, named and dismantled

This is the most persistent tourist fraud in Thailand and it has run in essentially the same form for forty years. The script is fixed. Near the Grand Palace, Wat Pho or another major temple, a pleasant, well dressed English speaking stranger falls into conversation and mentions, with apparent regret, that the site is closed this morning for a Buddhist ceremony, a royal visit, or a private government function. He is helpful. He knows a driver. A tuk tuk appears immediately and offers a tour of other temples for a nominal fare, twenty or forty baht, which no honest driver could accept.

The tour makes a stop, always, at a gem showroom described as government approved, or as a factory holding a one day export promotion, or as a duty free window that closes today. Inside, the sales approach is unhurried and plausible. There are certificates. There is a story about the stones being worth several times the price at home, and often an offer to help you resell them, or a claim that another customer buys at these terms regularly. The stones are typically low grade natural material, synthetic corundum, or glass filled composites, sold for many multiples of their value. Payment is by card, and the sums are large.

Every element of it is false, and the falsehoods are easy to state. The Thai government does not own, run, approve or endorse gem shops, and no such designation exists. There is no government export promotion on gemstones for tourists. The Grand Palace does not close for the reasons given; it keeps published hours and closes for genuine state occasions that are announced. No legitimate business pays a driver to bring a stranger to its door. There is no arbitrage in reselling retail gemstones abroad, and anyone describing one is describing a fraud. And a certificate produced inside the shop that sold you the stone is not a certificate in any meaningful sense.

The defence is entirely straightforward: never buy a gemstone from a shop you did not choose before leaving your hotel. That single rule defeats the entire scheme, because the scheme depends on the buyer being delivered rather than arriving. If a stranger tells you an attraction is closed, walk to the entrance and check for yourself. If you have already bought, contact the Tourist Police and your card issuer immediately rather than after you fly home, because both routes narrow quickly with time.

How a serious purchase is actually arranged

When a client asks our office to help with a significant stone, the sequence is the same every time and it is deliberately slow. We establish the brief first: species, size range, colour, budget, and whether the stone is for a specific commission. We approach dealers we have transacted with before, on the client's behalf, and stones are brought to a private room, frequently at the client's hotel, rather than the client being taken around showrooms. Nothing is decided in the room. Shortlisted stones go to an independent laboratory, and the client sees the report before the balance is paid. Payment is by bank transfer against a proper invoice in the buyer's name.

Two further points that clients raise. First, commissioning: once the stone is certified, Thai workshops will set it to a drawing to a very high standard and at a cost that makes the whole exercise worthwhile, which is the strongest argument for buying stones here at all. Second, export and the return leg: keep the invoice and the laboratory report together, declare the purchase where your own customs rules require it, and remember that a certified stone with clean paperwork is straightforward at a border while an expensive stone with no documents is not. Our guide to carrying purchases home sets out the process.

Verify any gemstone independently before payment. The Gem and Jewelry Institute of Thailand, a public organisation under the Ministry of Commerce, the Asian Institute of Gemological Sciences and the Gemological Institute of America laboratory in Bangkok all issue independent reports, and the Institute also publishes a list of shops in its own certification programme. If you believe you have been defrauded, contact the Tourist Police on 1155 and your card issuer without delay.

This briefing is general information, not legal, tax or investment advice. Thai rules change frequently and individual cases differ. Verify current requirements with the relevant authorities, including the Immigration Bureau, the Board of Investment, the Land Department, the Department of Business Development and the Revenue Department, and take advice on your own facts before acting.