Preheat oven to 400˚F (200°C). In large bowl, whisk together flour, baking powder, baking soda and salt. Cut butter into flour mixture using pastry-blender or rubbed with fingertips until mixture resembles coarse meal. Add apples, bacon and thyme; toss to combine.
Pour in buttermilk. Stir just until moistened. Do not overwork dough. Transfer to lightly floured board. Gently knead just until dough comes together. Pat into 1-in. (2.5-cm) thick slab. Using 2.5-in. (6-cm) round cutter, cut rounds; re-roll scraps and cut again for total of 12 biscuits.
Place biscuits 2-in. (5 cm) apart on parchment paper-lined baking sheet. Brush tops lightly with buttermilk. Bake 15 to 18 min. until golden brown. Serve warm or at room temperature. (Baked biscuits can be cooled, wrapped tightly and frozen up to 1 month, before thawing and warming to serve.)
Substitute bacon with 1 cup (250 mL) shredded Cheddar cheese.