Can you crochet a hat using 1 ply yarn?

I bought 1 ply yarn because it's very beautiful and I wanted to make my husband a yamulke. When I tried to make it using an E hook, it seemed a bit small. I then tried again using a G hook but the circle kept curving. Do I need to use a larger hook (J for example) or stick with a smaller hook since the yarn is so thin? Does anyone have a yamulke pattern??