Tiki has one perspective, but it may end your marriage. I also picked up on your openness and commitment to your marriage. Guys cheat because they are giving in to fantasy and the pursuit of excitement. Its so easy to do this in Asia that it almost seems normal. He probably doesn't like sneaking around and lying to but is afraid to tell you because you will be angry or make him feel ashamed etc. If you are wiling to explore alternative sexual fantasies with him, it might open up more honest discussion and end up working out for everyone. Sex workers are a health risk, and it's understandable that you are upset about that, but emotionally its probably better than an affair with a woman at work. Hope you work it out.