Intertrigo is that red, burning rash that happens from moisture and friction. Something I call "chub rub".
Aside from good hygiene, the goal here would be to keep the area dry and reduce the friction.
When my son had it, the doc had him sit exposed under a lamp. Me, I just used Gold Bond powder. That always seemed to do the trick. They do make something called "monkey butt powder", same principle. If I really needed to dry it out, I just used a hair dryer on low setting (you do not want high heat in tender areas).
If you think it's truly a fungal infection, you may need your doctor to diagnose. There are also anti-fungal powders out there. I would not recommend a cream/ointment because the causative factor here is moisture. Why would you want to introduce more moisture?