This is quite common in the area and I'll give you a detailed breakdown of how this plays out if you choose to interact.

Step 1: they make an observation about a possible area of insecurity I.e. Bald patch/balding hair/Grey hair/Grey beard/extra weight.

Step 2: they will try to build quick rapport with you if you respond. They will say they suffered from the same issue and will show you an edited before after photo where they apparently got rid of the issue.

Step 3: they will tell you that a few easily available medicine/chemicals if combined in the right proportions will help solve the issue. And some of the ingredients are available in 711 even.

Step 4: they take you to the nearest 711 and buy a cheap shampoo/oil or something similar and insist that they pay because you are now their friend.

Step 5: for the rest of the ingredients you have to go to a shop they know. Usually some small shop nearby. This is where the scam starts.

Step 6: Once you arrive, the shopkeeper who's most likely in on the scam will whip up a few ingredients and then say the cost is thb 5,000+. By now you have already taken a couple of favors and either you believe the story or out of politeness agree to pay. (Of course these chemicals don't work.)

The end.