Well, how to make dreads with thin hair. The best way to do it is to leave a little bit of the root before you actually begin your twisting, but you don't want to twist all the way down to the root when your hair is really thin.
You want to leave just a little bit of root, so it looks a little fuller and it has some support before you begin the actual twist and pin, because once you start twisting and pinning thin hair or hair that is thinner, it gets a little weak and the dreads look a little sparse.
So you definitely want to be conscious of the fact when your hair is a little thinner that you want the actual roots to look a little fuller. So my answer would be to leave a little of the root, so that way you have a little bit more support and a little bit more fullness. That's how you can get your thin dreads to look a little fuller.