Tourists at Chatuchak get shorted on change and can't prove what they handed over
A tourist handed a 1,000 baht note for a 500 baht pair of shoes; the vendor said she received 500, and a second man backed her up. The tourist felt there was nothing to do. The thread had 118 comments and 114 upvotes.
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5 ways to tackle it
Hardware and sensors
Till Mirror: a small screen at the stall that shows and says the note handed over
A Raspberry Pi camera over the cash tray reads the note a customer hands over and shows 'received: 1,000 baht' on a small screen facing the shopper, and says it aloud. Honest vendors get a way to prove they were not shorted, and shoppers see the count.
Build with Raspberry Pi, Pi camera, small LCD, speaker, Claude vision or a note classifier
Hardware and sensors
Change Wheel: a printed cardboard slide chart that shows the change due
A pocket-size card with a rotating wheel: set the price, set the note you gave, and the window shows the exact change and which notes it should be, color-coded to the baht notes. It works with no phone and no signal, and a stall owner can see you are checking.
Build with Laser or paper printer, cardstock, brass fasteners, generator script for the wheel PDF
Camera and vision
Note Snap: photograph the notes before handing over and see the change due
The shopper types the price and snaps the notes before paying. The AI reads the note values, saves a timestamped photo, and shows the exact change due, so there is a record if the count goes wrong.
Build with Claude vision, PWA, local timestamped photo store
iPhone and Android app
Baht Dojo: a 3 minute game against a fast-talking vendor that trains your eye on notes
You play a shopper at a busy stall: a vendor hands back change quickly and you tap 'right' or 'short' before the timer ends. It teaches note colors, the habit of saying the amount out loud, and what 1,000 baht looks like against 500, with a score to beat.
Build with PWA game, Claude (vendor lines in several languages), baht note images, TTS
Web portal
Count Aloud Kit: honest vendors print a stall sign, price tags and a rating QR
A vendor enters what they sell and gets a printable A4 sign saying 'we count change out loud', price tags in five languages, and a QR where tourists rate the stall by section and number. It gives honest stalls a visible way to stand out from the stall that shorted the tourist.
Build with Next.js, Claude (translation), PDF sign generator, QR code, Supabase
What people reported
r/ThailandTourism: short change at Chatuchak, vendor and bystander denied it
reddit.com