When you pair a strong personality with a communication disorder like autism, you can end up with a lot of spectacular show-downs. The child has definite ideas of what they want their world to look like, how they want people to behave, how they want situations to turn out, but they don't have the communication and social skills to do it in a "civilized" way .... so you get loud tantrums and melt-downs over seemingly trivial events. Adults around them often respond by becoming more unbending, drawing the boundaries in closer, giving less leeway and requiring a higher degree of compliance to every rule. Paradoxically, the tighter the rules, the farther out of bounds the behaviour can go.
To save sanity on all sides, I'd like to share an approach I've found useful:
First, do a little research by observing typically developing children (especially those who are strong-willed and opinionated). Really listen to the content of what they say; pay attention to how much time they spend talking about what they will do, what they won't do, what they might do, why they can't follow your direction right now, why they want to try a different way, why they need to dress like a cowboy this week ..... You'll discover that language is the civilizing factor, and that typically developing children are frequently allowed to bend and break the "usual" rules (without having to resort to negative behaviour), if they can give a plausible reason or simply fatigue the adults with verbal negotiation, and that the best verbal negotiators are generally viewed as the most socially mature (even though they might not follow the rules as closely and carefully as their quieter peers). It's normal and developmentally typical for young children to try to modify the rules of their world - they step up in social maturity as they learn what strategies work and what ones don't.
Next, you need to find out the perspective of your child with autism - no information is more important when you're trying to find solutions to difficult behaviour, but figuring it out can be very difficult when a child is young and has weak communication skills (even the most verbal ASD child will suffer language break-downs when the topic is emotionally charged). This is where drawing techniques are invaluable. Get big paper (or a big chalk board or a big white board) - you'll need lots of space for adding details. Then sit down (or stand, or take breaks between laps around the room) and draw a "starting scenario" - maybe it's the physical set-up of the child's classroom: