Preheat oven to 400 degrees. Spray a baking sheet with cooking spray. Set aside.
Make Turnover Filling: Pour the oil in a large skillet over medium heat; add hash browns. Cook, without stirring for 7 to 8 minutes or until brown and crisp. Turn the hash browns over and cook for an additional 4 to 5 minutes or until brown.
Stir in the bell pepper and onion mix; cook, stirring occasionally, for 3 to 4 minutes or until just softened.
Stir in the chicken, thyme, and 1 egg. Cook, stirring frequently, for 3 to 4 minutes or until the egg is just set. Check the seasoning, adding salt and pepper as needed.
Assemble Turnovers: On a slightly floured work surface, roll the sheet of puff pastry out into 12x8-inch rectangle. Cut the pastry in half lengthwise then into thirds crosswise, forming 6 squares.
Divide the filling evenly among the 6 squares, leaving a 1-inch border all around. Brush the border with beaten egg; fold each square into half, forming a triangle and covering the filling. Crimp the edges with a fork to form a seal.
Bake and Serve: Place the turnovers onto the prepared baking sheet. Bake for 10 to 12 minutes or until golden brown.