Recommendations to help stop the chaffing rash that occurs in the crevices of the crotch area due to incontinent absorbing underwear?

Father-in-law has dementia spends most of his time in bed, but gets up to eat and bathes daily, and is changed throughout the day and night, so we believe his chaffing and rash is a product of his absorbent underwear. We have tried various products to remedy the problem the rash continues, though we pay special attention to bathing the affected area(s).

Would appreciate any/all suggestions and or recommendations