Step 1:
The other side of this 11x11 centimeter paper is white.
Fold over the two outer lines first.

Step 6:
Press inwards.

Step 5:
Glue the edges together and open the model, see arrow

Step 3:
Prefold in half, then over the two diagonal lines

Step 2:
Fold in half

Step 4:
Fold the corners inwards over the prefolded lines (Make the same folds on the backside, mirrorwise)

Step 7:
Fold / bend the top of the hat downwards and fold over the yellow line (all around the model).

Done!
This is a short video tutorial for making the Santa Hat:

Pictures: Origami Santa Outfit with hat, christmas dress and black belt.