I was going to say that the twice-fried pork belly is what makes this dish appealing, but quickly realized the inaccuracy of that. If it's the crispy pork belly I'm after, I might as well make or buy some Chinese-style crispy pork belly, eat that, and call it a day. But, no. What makes this dish one of the most popular at made-to-order street food stalls and rice-curry shops in Thailand is the fact that all of the ingredients work together to create something greater than the sum of its parts.
To make things easier for you, don't make your own crispy pork belly; buy it instead. I hope there's a Chinese barbecue joint or a Chinatown where you live as those are the places where Chinese-style roasted pork belly (siu yuk) can often be found. If not, replace the crispy pork belly with the same amount of thinly sliced pork loin. It won't be the same, and it can't be called khana mu krop in the absence of mu krop (crispy pork), but it will be delicious regardless.
Those who don't like spicy things can omit the fresh bird's eye chilies. But I'd like to, if I may, encourage you to use them. They really make a difference to a rich, fatty dish such as this. If you're very sensitive to the heat of fresh chilies, perhaps you can add just a couple and lightly bruise them instead of slicing or chopping them.
This dish is usually served with rice but is also excellent atop blanched egg noodles.