Bangkok 8 by John Burdett
I've have had my eye on this book for a long time and it was recently lent to me by a friend. (See his review)
I have to say that this is one of the most engaging books I have read in awhile. The setting and details are novel and engaging. You become wrapped up in this story of a low ranking Thai cop pursuing the killers of a US Marine among the Bangkok underworld of sex and drugs. I felt it was a little unfortunate that the ending got out of the authors control. That complaint is minor, though, and I would heartily recommend you check this one out.