In a large bowl, whisk together flour, baking soda, baking powder, sea salt, cinnamon, and nutmeg. Set aside.
In another bowl, mix together 1/2 cup white sugar, pumpkin puree, butter, brown sugar, and vanilla until smooth and uniform.
Combine wet and dry ingredients and mix until a dough forms. Cover and refrigerate for 30 minutes or more.
Preheat oven to 350 degrees. Mix remaining sugar and chai spice together. Spoon out dough and roll into 1 1/2-inch balls. Roll in chai-sugar mixture then place on a baking sheet lined with parchment paper about one inch apart.
Bake for about 12 minutes. Edges should lightly brown but tops will not brown.
Cool on pan for about 10 minutes then finish cooling on rack, if desired.