When I was thinking about doing the same thing a couple of years back, what really hit me square in the face was the fact that alot of the people who are there year in and year out with the same bar(s). Generally don't , make all their money from just the bar. And if they do, they have pretty specific (return) customer bases.
There are the easy to see examples of this with other BM bars here. I wont mention any specifically as its not my place to say. But any real period of time in Patong and you can work out some of their specific 'regulars', to put a british pub term in, that keep certain bars ticking-over.
Of course it is possible to have a bar that makes money, but when it comes down to it, its purely based on where the bar is, and the amount of foot traffic that regualr enter/pass that space. But of course, these bars that are more likely to make money, any gonna cost more from the start before rent even comes in to it.
Then there is problems with changing tastes in soi's, low season's and as Crustasian points out, the fact that the whole tourist market is changing (rapidly, from my experience last trip!). So you may have to be lucky that you get a bar in the right place, or you can predict a new trend occuring.
I, of course never went through with buying a bar for many reasons. And I know that there are many other BM's who know the bar scene, and how to give yourself the best chance at making money from it. Which certainly does not include me!
Best of luck with what ever you decide.
