Bring a large pot of water to a boil. add pasta and cook according to package directions until al dente. Drain and rinse under cold water until cooled. Set aside.
While the pasta cooks, place bacon in unheated skillet. Then cook until crispy over medium heat for 8 to 10 minutes, turning frequently. Remove to a paper towel-lined plate to drain. Once cool enough to handle, rough chop the bacon.
To a large mixing bowl, add the pasta and ranch dressing. Stir until pasta is coated.
Add most of the tomatoes, lettuce, and most of the bacon to the pasta. Gently stir to combine and coat all the ingredients.
Garnish the top of the pasta salad with reserved tomatoes, bacon, and chives. Serve immediately.
If you're making this salad ahead of time to serve later in the day, prep all the ingredients beforehand and store in the fridge. Then mix together just before serving. This prevents the lettuce from wilting and will keep the salad tasting fresh.