I agree with Krav Maga. Muay Thai is a good art to know, but the problem is the lack of a ground 'game'. I use the word 'game' loosely, because in the street, there is no game. My only suggestion would be to stay away from submission grappling if you are worried about self defense. Submission grappling is based on rules. There are no rules if you are trying to save your life or someone else's. Kill, or be killed. Taking submission grappling to a life or death situation is a good way to get killed. Krav Maga or Jeet Kune Do would be my two choices. They teach lethal strikes...and try to finish the fight in the shortest time possible. That's what you want. No fluff. Throat strikes, groin strikes, eye gouges, whatever it takes. You won't learn that with submission grappling.