In modern MMA every martial artist knows, more or less, a basic Muay Thai striking. Thai Boxing is so much present inside the octagon that became an inseparable part of MMA. The popularity of Thai Boxing in cage fighting can be a curse - some people don't even realize that those are two different sports. To put it more precisely - people, especially in the US - see Muay Thai only as an addition to the UFC and not a separate sport.
Joanna Jedrzejczyk: There are just a few very successful MMA fighters with a pure Muay Thai background in the UFC and Joanna Jedrzejczyk is definitely one of them. She is known mostly as the mixed martial arts fighter but she is a former multiple Muay Thai and Kickboxing champion. She is a current UFC strawweight champion and she manages to combine a spectacular stand-up striking with a good submission defense. A lot of fighters that are good at striking are not as capable when it comes to ground work. She simply devastates her opponents with a diverse combination of powerful strikes and her takedown defense skills helps her to stay off the ground. Most of her bouts are very spectacular and just a pleasure to watch. She is a very dominant striker and a natural born fighter and she has the best Muay Thai in MMA competitions. Read more about Joanna Champion
Jose Aldo is BJJ specialist but he is mostly known in the UFC as a Muay Thai striker. His style resembles more of Dutch-style kickboxing than traditional Thai boxings thanks to his training with Andy Souver. He makes an extensive use of kick, knees and punches and not so much of elbow strikes which are characteristic to Dutch-style Muay Thai.
Karolina Kowalkiewicz Second best fighter in a women strawweight division also known, thanks to her appearance, as a Polish Princess. Don't let her sweet nickname and cute appearance fool you - she is a very gifted striker and she was the hardest opponent that Joanna Jedrzejczyk faced so far in the UFC. Her clash with Joanna Jedrzejczyk was probably the best example of a great Muay Thai in MMA fight.
Rafael Dos Anjos
A very aggressive fighter that adopted Muay Thai as his primary stand-up striking style which is a good addition to his BJJ grappling skills. He has got a decent UFC record of 25 wins and 9 losses (mainly by a decision). 2016 wasn't the best year in his professional career since he suffered two defeats (one by TKO) in a row.
Muay Thai is very popular in Brazil so it shouldn't come as a surprise that Mauricio 'Shogun' Rua is on my list. He makes use of Muay Thai in the octagon, although, he is not a pure Muay Thai striker and he combines it with some old-fashioned brawling. He is a type of a fighter that possesses extraordinary stamina and a brutal strength. He is one of those competitors - as opposed to GSP - that wants to knock out his opponent out cold and not just to win a bout on points. His fights are a pure pleasure to watch: most notably his first fight against Dan "Hendo" Henderson. Read more about Shogun Rua
Why is it useful to develop Muay Thai as your core style? The answer is simple: an average pro fighter in Thailand has got 150 to 250 professional fights under his belt before he retires and becomes a trainer (compare this number with Western boxers fight records and you will get a clear picture how competitive and physically demanding Thai Boxing is). Many aspiring fighters comes to Thailand to train to become complete stand-up strikers. To learn from the best and the most experienced fighters and to adapt a training regime that tolerates no shortcuts.