To make the dressing, combine mayonnaise, lemon juice, lemon zest, sugar and thyme in the bowl of a food processor; season with salt and pepper, to taste. With the motor running, add the olive oil in a slow stream until emulsified; set aside.
In a large pot of boiling salted water, cook pasta according to package instructions; drain well.
Heat a large skillet over medium high heat. Add bacon and cook until brown and crispy, about 6-8 minutes. Transfer to a paper towel-lined plate.
In a large bowl, combine pasta, bacon, avocado, lemon-thyme dressing, salt and pepper to taste.