1. This man is willing to risk catching and bringing home a disease for you to share. Can you really accept that he is that kind of person, and that he treats you with such disrespect?
2. Thailand is known as a major "sex vacation" destination. Once your husband arrives there, he will be bombarded with offers he may not be able to refuse.
3. He is lying to your face, repeatedly.
4. It's highly unlikely that he will stop his extramarital activities.
5. BDSM may be something he has experienced before.
6. BDSM is, for some people, a driving need, and it can become a habit, or even an obsession.
7. It may very well be that you have NO CLUE as to what your husband's desires, fantasies, etc. really are. He may be downplaying it all (to you, and to the hooker in Thailand) due to his "pride," and so that you can "accept" what he says he wants.
(Aside: How "proud" can a man truly be, if he goes to hookers in Thailand, in order to pay for and "submit" to their fake Domination?)
8. If you keep your mouth shut, and possibly even if you open your mouth, this situation will become the Elephant in the Living Room.

It's better to come clean and get it all out in the open, although HE may not come completely clean. Don't invest more of your time, your life, and your heart in him and in this marriage, when you have so many unanswered questions.