Think of hair as an accessory for your face, something that can accentuate the positive (or the negative if you have the wrong hair style). The following hair tips, in particular, can help make your thin or sunken cheeks look fuller and rounder.
Bangs help the eye move from side to side across the face, rather than up and down, and can give the appearance of fullness in the cheeks. If you don't already have bangs, consider cutting them to reduce the appearance of thin, sunken cheeks.
Long hair can also accentuate the thinness of your cheeks and make your face look longer, whereas a chin-length or even a shoulder-length hairstyle will give the cheeks a little more plumpness.
If your hair is a little bit longer than chin length, layers can also help give the illusion of fuller cheeks, especially shorter, chunkier layers that are closer to the base of your face. Layers create dimension and fullness, distracting from thin or sunken cheeks.
Finally, parting your hair in different locations can also make a difference. Experiment with a center part or a side part on either side to see if one or the other makes the cheeks look fuller.