I really can't think of any of the men who really fight with a Muaythai heavy style, Barboza and Aldo maybe but even then that's a stretch. Roundtree fights with a heavy Muaythai style, but at a pretty low level.
The Women have JJ and Valentina who show off high level Muaythai, there was also a Thai women who won recently with a very Muaythai based style.
Fighting in a Muaythai stance is asking for trouble in MMA with the take downs and lack of head movement, although it would counter the calf kick that is popular these days.