Market stalls and online sellers get fooled by sticker-swapped QR codes and fake slips

5 ways to tackle it

• Hardware and sensors

  Money Box: a speaker that says the amount only when the real bank alert arrives

  A small box on the counter listens to the shop's bank alerts and says 'received 150 baht from Somchai' out loud. A fake slip on a customer's phone cannot make it speak, so the seller waits for the voice before handing over the bag. It works with the stall's own bank notifications, no new account.

  Build with ESP32 with speaker, Android notification forwarder or bank webhook, Thai TTS clips

• Camera and vision

  Slip Scanner: hold a slip up to a phone stand and get green or red in one second

  The seller props an old phone on a stand. A customer holds the slip toward it, Claude vision reads the QR and the bank reference, and a slip verification API checks it against the bank. Green means real, red means do not hand over the goods.

  Build with Old Android phone, Claude vision, SlipOK or similar slip verification API, Next.js PWA

• Web portal

  Name Sign Printer: a sign beside your QR showing the exact name buyers should see

  The seller enters the PromptPay number and gets a print-ready sign: 'After you scan, your bank app must show SOMCHAI S. If it shows another name, do not pay'. The sign sits next to the QR. A pasted-over sticker shows a different name and the buyer sees it before paying.

  Build with Next.js, PromptPay QR generator, PDF sign template, A5 laminate

• Voice and phone

  Scam Drill Call: an AI phones you as a fake buyer so you practice saying no

  The seller gets a call from an AI playing a buyer: 'I paid 3,000 instead of 300, please send 2,700 back'. The seller practices checking the bank app and refusing, and hears a score and the exact lines to use after. Five minutes of practice before the real call comes.

  Build with Twilio Voice, Whisper Thai, Claude, Thai TTS

• Hardware and sensors

  Stall Siren: one big button that flashes a light at every stall in the market

  Each stall has a small lamp. When one seller hits the big red button after spotting a fake slip or a swapped QR, all neighbor lamps flash and a phone photo of the scammer goes to every stall. A market of 30 stalls protects itself in seconds.

  Build with ESP32 with LoRa or Wi-Fi, LED lamp, arcade button, Telegram or LINE push for the photo