To prepare the dressing- in a food processor combine mayonnaise, lemon juice, lemon zest, sugar, and thyme. Season with salt and pepper to taste. Turn the blender on and add the olive oil in a slow stream until emulsified. Set aside. Bring a large pot of salted water to a boil. Cook pasta according to package directions. Drain and set aside.
Heat a large skillet to medium-high heat. Add the bacon and cook until brown and crisp (about 6-8 minutes). Drain on a plate lined with a paper towel.
In a large bowl combine the pasta, avocado, bacon, lemon-thyme dressing, and salt and pepper to taste. Serve right away and garnish with fresh thyme.