When you go to pay make sure that you weren’t charged for something twice. Normally they insist on giving you the receipt, but if they don’t then be suspicious. You may have bought a “gift” for the checkout girl. Another scam is that they give you the wrong change and then pocket the difference. This is sometimes done in Pattaya where foreign tourists might not be familiar with the banknotes. Give them a 1,000 Baht note and they give you change for 500 Baht. Of course, it might not always be a scam as Math is not always their best subject. I’ve been given too much change before!
It just shows you that you do need to be aware of the prices of items when you buy them at places like 7-Eleven and Big C. Have you had any bad experiences like this in shops?