From the photo, there is a noticeable fold/fullness beneath the chin when the head is flexed downward. However, this position can naturally exaggerate the appearance of a double chin, so the key question is how the area looks with the head in a neutral position. Because this developed after a sliding/structural mentoplasty, I would not automatically assume that excess fat is the only issue. The appearance can potentially be related to a combination of submental fat, skin or soft-tissue laxity, scar tissue, and changes in the relationship between the chin and the tissues underneath it after surgery. If there is a relatively small amount of excess submental fat and the skin has good elasticity, submental liposuction could make a meaningful improvement. However, liposuction cannot tighten significantly loose skin or correct a deeper structural problem. In some post-mentoplasty cases, removing fat alone can actually make an indentation or contour irregularity more apparent if the underlying issue is soft-tissue support rather than fat. If the fold is present even when the head is in a neutral position, I would be more interested in determining whether there is scar tethering or altered soft-tissue attachment beneath the chin. Depending on the findings, treatment could range from conservative submental liposuction to a more involved revision addressing the soft tissue or platysma. The original surgical technique and exactly how the chin was repositioned would also be important in deciding this. I would therefore be cautious about proceeding with liposuction as the only treatment without first determining what is creating the fold. Lipo may be enough if the problem is primarily localized fat, but if the fullness is primarily structural or related to postoperative soft tissue, something more than lipo may be necessary.