There is really no such food source that can make your hair thick, genetics play the major role in this.
However, I'm lucky enough to have thick dark hair that grows rapidly & my personal big 3 are:
Protein: chicken, turkey, eggs, etc - good quality protein intake is necessary for hair growth otherwise you end up with soft brittle hair that alot of women have.
Green veggies: pretty obvious choice here since they're packed full of vitamons, minerals & antioxidants - specifically vit A, C, iron & calcium for hair quality.
Salmon/omega 3s: easily the best food source/nutrient for hair in terms of scalp health, hair condition & strength.
Again, nothing special here since most guys should already know that protein, veggies & omega 3s are good for you