You can do this, but the quality of the thawed and refrozen hash browns will not be as crispy when refrozen and they will hold up for a shorter time period, no more than just a few days to a week. Frozen hash browns are flash frozen very quickly and this is hard to replicate at home, so the potato has a tendency to be soggy.

Another option you might try is to use a package of dehydrated hash browns. That way, you can add water to make how many you want, while the amount that remains unhydrated is still shelf-stable. These products can be found in the grocery aisle where the instant mashed potatoes are sold.