Preheat oven to 425 degrees. In a large bowl, combine flour, thyme, baking powder, salt, and baking soda. Using a fork, pastry blender, or your fingers, incorporate butter into flour mixture until mixture resembles coarse meal.
Mix in buttermilk until a sticky dough forms; you may need to add up to 1 tablespoon more buttermilk.
Drop 8 mounds (each a scant 1/3 cup) onto a nonstick baking sheet; lightly pat tops to flatten slightly.
Bake until golden brown, 15 to 20 minutes, rotating sheet halfway through. Transfer to a wire rack to cool slightly. Serve warm.