How to reduce stitch visibility? Sewing Machines Parts and Sales in Los Angeles

My tailored seams are a bit too visible on inside pant legs. I’ve tried to reduce stitch visibility by decreasing the stitch distance, but to no avail.

Current (inadequate) technique: I tailor my clothes by turning them inside out, grabbing a fold of fabric, and sewing over it so as to slim the clothing article down. I typically start with a loose straight stitch before closing with a tight zigzag stitch.