Oh, glad your here, I went through the same thing. I've done ITF Tae Kwon Do for the past 10 years of my life and am still going to compete for about a year or so. I've been kickboxing for about 4 years, muay thai for 2 years and mma for 1 year.
It really depends on the fighter. Me, I'm a terrible athlete, I'm clumsy as heck, I always stumble and trip over myself, I run into walls, my vertical isn't fantastic, I'm not quick I'm not fast. However, in Tae Kwon Do fights, I always pictured things for like a kickboxing fight. The hardest thing to do is in fact getting rid of the point fighting mentality. That's gonna take a lot of work and it'll work itself in over the next year.
Another is the pace a muay thai fight is fought at compared to a Tae Kwon Do fight. Tae Kwon Do is much faster compared to Muay Thai however Muay Thai is MUCH more devastating when compared with punching and kicking also including elbows and knees. In Tae Kwon Do you can somewhat hold your kicks back although most people don't but in muay thai if you hold a kick back your getting thrown to the mat.
The angles for Muay Thai and Tae Kwon Do are similar yet when broken down, fairly different. There's really certain things you can and can't throw in each art.
The ring is another thing. Tae Kwon Do you have an open square, muay thai you have a closed ring.
No warnings and deduction of points really in muay thai that's in tae kwon do, and less ref interference.
Don't try any 180 hook kicks. Keep your kicks basic in Muay Thai.
That's about it, good lucky buddy.