What's wrong with perpetual laughter? Children are supposed to find joy and humor and wonder in everything. You know who else "laughs at everything?" The Dalai Lama. And supposedly Buddha. Have you not seen numerous reproductions of his jolly fat belly and his peaceful laughing countenance?
Seriously though, before you interpret the laughter as outright insubordination or lack of understanding about actions or something that is an insult or challenge directed at you and your partner - take a second like Marm said to evaluate what the laughter actually is, where it is coming from, and who it is directed, if anyone.
Honestly, kids will have their joy and laughter beaten out of them soon enough by life and other people, I'm totally projecting but thinking as an ENFP who used to be a very happy, smiling, laughing child that your child would be better served as a person and also appreciate it more (both now and later in life) if you tried to preserve that connection to joy and wonder if that is indeed where the laughter is coming from.
Then again, I am probably more hands off than other people and I do not have children of my own.
Having looked after children though, and in particular one special needs child who had learning and behavioral problems - she ALWAYS laughed. Laughed and cried. But mostly laughed. Her speech developed at a much slower rate than her peers and she may have had hearing problems as well (parents were unsure at the time), I was never sure exactly what she was saying - I don't think anyone did 100% of the time. She mostly danced and vocalized to express herself. But she and I got along well. When she would do something bad - throw dominoes at people, take things, mess up papers on a desk - everyone in her family was sure she knew on some level that it was 'bad'. And when she was scolded she would laugh and sometimes run away. Sometimes if she was punished she would start out laughing and laughing then start crying then eventually start laughing again.
In that case ^^ I don't think her laughter per sae had anything directly to do with her behavioral issues, as in, laughing less would not make her listen better or follow directions better.
Basically, the root of laughter is so different in children and unless it is hurtful or mean or distressed or manipulative laughter, I dunno, I'm kinda of the mindset to let it be. To me laughter = joy/wonder/gratitude and those are really GOOD things that you want your children to have. How old is your child, as well? Some kids just aren't at the age to comprehend that they are being 'disrespectful' or 'bad' by laughing. I was imagining from your OP that your child is no older than 7 and more toddler aged? If we're talking 13, whoa I have a different answer for you!
Sorry if that answer was way too hippie and not enough practical for you.
One of them is a holy terror on his brothers and gets in trouble with his parents all the time (and he does *not* like being restricted in his adventures like that), the other bumps his head against something that would send most kids into a hysteric crying frenzy, and he just goes 'ouch. *giggle*' and moves on. He's really easy that way, but a holy terror to teach not to hurt his ExFx sister by swinging things at her, as he finds her response to be rather amusing and puzzling (must push that button again!). And him getting in trouble for that? Oh well, that's part of the price you pay for that type of research 
