In a large ziplock bag combine chicken thighs, smoked paprika, ancho, chili powder, chipotle, avocado oil, salt and pepper. Remove excess air and seal. Massage chicken and shake bag to combine all ingredients. Refrigerate chicken and allow to marinate for 30 minutes minimum.
Preheat grill pan on medium-high heat.
Remove chicken thighs from ziplock bag and place on grill. Top grill loosely with a sheet of foil. Cook thighs for 12 minutes, flip and cook for an additional 12 minutes or until cooked through.
Cut ends from baguette and cut loaf into 2 6-inch pieces. Slice each 6-inch piece open lengthwise. Layer each sandwich with 1/2 cup arugula, 1/2 sliced tomato and top with 2 chicken thighs.