Just what I think, but I could be wrong:
The Thai stance is a little bit too upright for MMA. To properly sprawl, your knees need to be slightly flexed, and you should be on the balls of your toes.
Also, because the majority of the weight is on the back foot, it makes the sprawl even harder.
I don't even like the Thai stance for stand-up to be honest. Keeping your weight off the front foot allows you to check faster, but if you miss that check, and your weight's off the front foot, that kick is going to effing hurt. When a strike connects with a relaxed muscle, that's when it's the worst. Of course, the Thai are just that damn good that they can make that check, and if they miss it, they're fast enough to shift their weight or do something else with the leg. But for noobs like me, I like to keep the weight even as possible on both feet, so if I miss the check I can at least flex my quad hard and try to take the shot.
I don't like keeping my hands high and wide. I like keeping them in closer and at about eyebrow level (but when I get closer, the hands go down to cheek or chin level). You need to be able to defend high kick attempts, but in MMA a high percentage of the attacks are going to be takedown attempts, and you need your hands to fight a takedown.
