Do Muay Thai fighters break their legs?
Muay Thai fighters do not break their bones, though. Instead, they cause micro-fractures that fill with calcium and become denser and stronger over time.
Is Muay Thai better than Krav Maga?
In general, Krav Maga is better for self-defense than Muay Thai simply because it was invented for the sole purpose of defending yourself. But, having knowledge of either of the two will help you a lot when it comes to self-defense.