'they would just ram their head into your face.' - the definition of a headbutt.
Stop trying to pretend you said anything else, what you said was clearly a headbutt. Either way, it's irrelevant. A thai fighter who knows what he's doing, or really anyone with solid clinching experience will have a strong enough grip and good enough technique to block that sort of ridiculous move you just described. As I said previously, the elbows/forearms act like a pincer on the neck, very little movement can be made at the neck, not nearly enough for a headbutt. The only way to escape a proper clinch is through good technical escapes, not brute force. As soon as you move your head forward you're off balance and they'll swing you to the side or pull you backwards and you'll have a knee in your face. You don't understand the basic mechanics of a proper thai clinch. Everything you say is just a simplistic 'hurr, just hit him with the head' like some magical way of fighting against a clinch that requires decades of experience to master. No one without thai clinch experience will be able to escape against a proper thai boxer, they don't have the technique.
You keep going on about your experience and 'sparring' and how I'm an 'keyboard warrior' but I'M the only one using logic and describing techniques and how they would work. On the other hand, YOU are the one who basically pulls 'techniques' or scenarios out of nothing (people with strong necks can just 'power out' of thai clinches etc.). YOU are the one who said that someone who plays rugby will have enough clinch experience to avoid being destroyed in a clinch by a thai fighter. And finally, YOU are the one who earlier claimed in this thread that Judo was a ground-based martial art. Now am I the keyboard warrior here or are you?
EDIT:
Just FYI, a maul is where the ball is held up and the players try and rip the ball from the other team. The ball isn't on the ground, it's held in a player's hand. There's no reaching down. I used to play rugby, I know.
EDIT:
http://www.youtube.com/watch?v=1KcCu13AJY4This is a maul. That's an awful way to counter judo. You're leaning on your opponents, no balance at all. You'd be MORE easily thrown if someone tried that on you.