Jun Pbad Gleeb or Pboy Gug จันทร์แปดกลีบ, โป๊ยกั๊ก
This is a classic Chinese spice that, in Thai dishes, is added primarily to soups. For the soup, you will want to add the whole seed pod instead of it ground up. While you don't eat it, it looks pretty in the dish while adding the flavor.
This is one of the components of Chinese five spice.
Star anises are available at most Asian markets and Indian/Pakistani stores.