Preheat the oven to 425°F.
On a baking sheet, place the bacon slices about 1⁄2 inch apart. Put the sheet in the preheated oven. Cook for 10 to 15 minutes, or until crispy.
Set aside to cool. Maintain the oven temperature.
In a large skillet over medium-high heat, melt the butter. Add the spinach and garlic. Cook until the spinach wilts, about 2 minutes. Remove the spinach from the skillet. Set aside.
Chop the cooled bacon into small pieces.
In a large bowl, mix together the cream cheese, sautéed spinach, and chopped bacon.
On a at surface, lay out the chicken thighs. Spread the meat open so the thighs lay at.
Place an equal portion of the cream cheese mixture on each piece of chicken.
Top each with the Swiss cheese, equally divided.
Close the thighs. Secure with toothpicks. Season with the salt and pepper.
Place the chicken thighs in a baking dish.
Put the baking dish into the preheated oven. Bake for about 18 minutes with a meat thermometer, check the internal temperature. It should reach 165°F before serving.