Just back from staying a week in Khao Lak. Stayed in a small guest house/resort called Fasai . Similar (but worse) than the 'napkin story', upon getting the final bill it was explained that we got a cheaper price due to my Thai wife booking holiday (NOTE 1 : duel pricing) we duly paid the bill.
This was a large group booking as 7 people (inc my 2 kids) were over from U.K. for a Thai wedding the following week.
Upon getting to Phuket airport and waiting at the boarding gate, we were approached by 2 (friendly) policemen who informed us that we had underpaid our bill by 41,000b!!! ! (NOTE 2: get a fully detailed reciept). After visits to ATM& taking all my guests money, we paid bill with a view to sorting it out after we get back 'home' in Isaan. This error had the following 'knock-on' affect
1) we all (9) missed onward flight.
2) my guests/kids had to return to U.K. Penniless a week early.
3) we were left with a wedding/ huge party arranged & no bride or groom. This cost me about a years salary!
4) next day Hotel returned 33,000b & said their error.!!
Just a heads up about Fasai at Khao Lak. Lovely area BTW.