As was indicated earlier, describing karate is difficult, as there are so many styles. Regardless, here is what practitioners might typically see from the two different styles.
Karate: Karate is primarily a stand up style of fighting, although throws and fast submissions- not really ground fighting, but hitting the ground and immediately moving into joint locks- are taught, often to a minimal extent. Most karate styles also teach some standing joint locks, wrist grabs, etc.
Karate stand up is generally characterized by mostly straight punches (reverse punches) and a variety of kicks. Though karate styles do teach elbow and knee strikes, these are not typically used in tournament action; so perhaps they are not as practiced as let's say in Muay Thai. Then again, it does depend on the style of karate.
Regardless, in and out movement/footwork is often demonstrated by practitioners. Karate fighters tend to be elusive. They also tend to put a lot of focus on powerful strikes designed to incapacitate quickly. By and large, most karate styles profess to be self-defense oriented, meaning that the main focus is to end fights quickly and without injury.
Karate fighters also tend to keep their hands lower in their stances, perhaps as a result of the types of sports tournaments they engage in. For example, point sparring (no contact or mild contact sparring) does not put a lot of emphasis on whether a strike lands to the head or body. Further, Kyokushin style tournaments tend to disallow punches (not kicks) to the head, perhaps fostering this type of stance, as practitioners may feel more confident moving their hands up quickly to their faces to defend against kicks, which tend to be slower than punches. Karate fighters also often utilize wider stances, and may, at times, be proficient from both a southpaw and standard slant, since this is something that is focused on. There is also a tendency, perhaps because of the aforementioned as well, to not tuck the chin (something boxers teach in order to lessen the jarring action to the face when strikes connect there).
In terms of round house kicks, karate fighters tend to teach to hit with the ball of the foot, not the shin. But again, this is not always the case, depending on the style/teacher. Their kicks also tend to be quicker and more precise, but less powerful than those in Muay Thai.
Muay Thai: Muay Thai, like karate, is primarily a striking style. The difference is that in Muay Thai, which is both a self defense art as well as a sport (Muay Thai kickboxing), the focus is clearly on using all eight limbs- shins, elbows, knees, and hands- as weapons.
Muay Thai fighters are highly adept at elbow strikes, boxing style movement (side to side), and a variety of kicks. What sets them apart further, however, is their ability to compete inside in a stand up fight. They do this by using the clinch, in essence grabbing the back of an opponent's neck and then utilizing knees inside to their opponent's detriment.
Thai fighters are also known for keeping their hands higher than karate stylists, like a boxer, and delivering roundhouse kicks, particularly to the legs, that connect via the shin. Thai fighters can often be seen toughening their shins by kicking trees.
Some Thai schools do teach a level of takedowns and grappling. But in this day and age, Muay Thai has mostly become about kickboxing and the sport.
So now that you know what these two primarily striking styles are about, check out.....
Some of the Great Karate vs. Muay Thai Matches of All-Time
Check out some of the greatest Karate vs. Muay Thai matches below by following the links.