Tuk Tuk drivers throughout Bangkok supplement their income with commision from jewelry and tailor shops. By geting farangs inside a store, they are issued gas vouchers for their effort, if the farang goes for the hard sell, the Tuk Tuk driver receives a bit of Baht.
All around Khao San Road Tuk tuk drivers wait paitiently for newbie backpackers to stumble into their trap...
It goes like this...
A Tuk tuk driver holding a map explains to the tourist that they will take them all over Bangkok to see the various Wats for a mere 10-50 baht (.25 - 1 US $). Cheap price to see the Reclining Buddha, Golden Buddha, and other sites refered to in tourist pamphlets distributed on planes and suggested itineraries in guidebooks.
Unsuspecting tourist thinks this is a fine way to get around and agrees to the deal.
At first Wat, a well dressed Thai man usually carrying a cell phone befriends the tourists, explaining to them that they are a policeman or some other official. Then a short pseudo tour ensues where the well dressed man explains how much money is made by purchasing jewelry in Thailand at a cheap price only to reap huge profits overseas. Sometimes these guys are with the original Tuk Tuk driver, or often they have another driver waiting if they get the tourist hooked (to take the tourist directly to the jewelry store). Sometimes the well dressed man will go for immediate "kill" by saying the Wat is "closed" and will open an hour later, "wouldn't some shopping be fun?"
Street smart tourists that look through these facades and stay on their tour all eventually end up at the stores anyway.
Original Tuk Tuk driver (after the tour when he has you far away from your original spot on Khao San Road) explains that he needs gas and that free gas vouchers are provided if you "just step into" a few shops... Kind tourist agrees. If you refuse, they will take you anyway, raise the original price for the Tuk Tuk or just drop you off.
The shop owners of the Jewelry and tailor shops try to sell you anything/everything at discount prices. It's awful.
Key is, learn quick and don't give in. If a driver approaches you the first thing they ask is "Where are you going?" reply, "just up the street". Second thing they ask is "How long you stay in Bangkok?" reply, "I've been here a month." the drivers immediately leave you alone at this point. If you absolutely need a tuk tuk, barter adamently, and don't give up set a price, repeat it and tell them to go just to where you are going, "NO STOPS!" they usually smile and agree.
If you want to have some fun, there are numerous ways to mess with the drivers, ask them if they know where you can do some shopping or just use your imagination. Remember though, these guys are just trying to make a living.