This is a fungal infection of the mouth, caused by yeast: Candida albicans...
Yes, the same culprit that causes yeast infection in adults! Normally Yeast exists freely on the body and in the mouth, but sometimes it grows out of control, especially when the immune system is overwhelmed. When that happens in the mouth, white patches develop on the tongue and the inside of the cheeks.

Oral thrush is a fungal infection caused by yeast: candida Albicans, it usually sticks on the cheeks.Kindly take him to see a doctor for drug prescription.