My brother's been taking Muay Thai for only a few months, he's not particulary skilled in. That being said, he's become significantly better at fighting than me and I don't think I would have a chance now. I think any martial art where you spar and specifically are forced to take hits to the face will give a huge advantage over the average person. I think people really underestimate how unprepared the average person is in fighting and it only takes practice to have a large edge over other people.
For the most part, it takes time to be really skilled, especially Muay Thai. I know some moves like.
Elbow
Knee to the stomach
Teep
However, I don't have too much experience in it
I do have a bluebelt in TKD and Shotokan Karate.
like Muay Thai footwork matters & so does having a good block
Be able to control your breathing. If you don't you're going to get tired very easily & you're more likely to be defeated by your opponent, which is really bad, especially if your opponent knows how to fight back.
I would advise to work the core of the stomach as well because it'll help you longer into rounds.
These were excercises I did during my time at Sovereign Martial Arts. The head instructor was Jose Di-Cervo(Diaz-Cervo)
Split for 13 minutes.(I was in my teens at the time)
Plank for an hour (Was also in my teens)
It was disciplined for it because I failed to write my report.
400 push ups
Rolling a heavybag back & forth, which was the worst excercise because that was the one you did after we exhausted
Here's their YouTube channel
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There are are Schools I went like
Christian Karate Institute the head instructor was Michael Morris. They taught regular Karate
Universal Martial Arts the head instructor was Damien Harley. I took mostly the TKD class. There were a few occasions that I took cardio Kickboxing.
World Class Martial Arts
Head Instructor Master Perry(never got his last name). I was mostly trained by instructor Myles
Now I go to Rare Breed MMA. The head instructors are Coach Emilio & Stephanie.
Edit
Haven't been as much shape as I was then, but that's another story.