Thin pork belly - braise?
Yes, you can braise it. How long well that depend on the amount of heat you apply to the pot. Not all stove and burners are equal in that the simmer on one may well be higher or lower. I would as normal for half and hour and check on the tenderest of the pork belly and go from there. Not the answer you want but it is a start. I never cook by time but by feel. I push " the flesh".
If you are cooking vegetables like in a stew I would cook the other items on there own so the texture and feel will be the same.