Whilst I never habitually encourage people to eat crisps, for diarrhoea relief I advise eating lightly salted crisps. The salt being sodium has the ability to dry up loose stools.
However it is imperative that you see a TICM doctor to get to the root cause of diarrhoea. Do not eat crisps long term as the salt will lead to retaining water in the body leading to sodium potassium imbalance. Therefore eating lightly salted crisps must never be for more than 48 hours.