One book by my favorite author, Paul Theroux, it is titled "Siamese Nights." The book is about an American businessman that is posted to Bangkok. It is a fascinating read about how a typical businessman can be taken in and have his life turned upside-down.
If you enjoy history, an interesting two part book series titled "The Falcon of Siam" by Axel Alywen is a sweeping historical read about Thailand's early kingdom. Another great book.