R.R.
Personally I would veer away from using "punishments" on children who wet themselves.
Children learn by imitation and natural consequences, while punishment is just an attempt to minipulate them to do what we want them to do, rather than guide them with *their* best interests in mind. I always ask myself- am I motivated by a wish to help my child grow and learn, or by my own frustration and inconvenience at their behaviour? The difference means teaching them to be manipulative vs helpful with others when they are older.
If your child becomes too engrossed in play, simple reminders throughout the day, as well as YOU reminding YOURSELF ("Oh, I'm so busy finishing supper but I REALLY need to go potty now so I don't have an accident) are GENTLE ways to teach your child. This may sound silly, but what WE do makes a huge impression on our kids. I find my 3.5 yr old solving his problems the same way I solve mine. Then, when there is an accident, remind yourself that a little mess in the pants is not worth creating negative emotions between your child and you. Make a song up about it to remind them- perhaps "This is the way we go to the potty, go to the potty, go to the potty; this is the way we go to the potty, so we don't get messy" to the tune of "Here We Go Round the Mulberry Bush" (this is a fav tune in our house and we make up all sorts of lyrics to it to "remind us")- and HAVE THEM HELP YOU put the soiled clothes in the wash. I have my son stand in the tub and I quickly wash him off- no extended fun or bath- and he stays in just a shirt and undies til his clothes come back out of the dryer to emphasize that when we wet our clothes they are not available for our use... but not in a punitive way. When they are dry, we'll put his socks and pants back on and sing our reminder song again.
Your daughter's laughter doesn't mean she is happy to upset you; rather, she probably doesn't have the emotional tools to deal with the situation... and even if it *were* a control issue, if you counter it by taking more control away (losing "privileges" or toys), you are in effect reaffirming the power struggle. If you think it is a control issue, evaulate whether or not your child may be feeling a loss of security and if so, what may be making her insecure? Or, are there more responsibilities/activities she is ready for that will give her a sense of mastery?
Does she need some more attention?
At 3.5 it would be highly unusual that a child would have an accident to "be bad"... take it as a sign that she needs help or affirmation, even if that affirmation is simply to go over potty basics again.