There are various and nice origami snowmen out there, but usually you have to add a separate hat on top. Here's a new design of mine of a snowman with a Santa’s hat folded from a single sheet of paper. Follow the diagrams you can download here or watch the video tutorial by Sara Adams to fold your own snowman.
You can use the snowman as a hanging decoration for your Christmas tree or glue it on a greeting card. Happy holidays!