Having thyroid removed - can I get the skin on my neck tightened through the same incision?

It is difficult to talk about unusual surgical option without series of photos or in person evaluation. It would be possible to remove some skin from the neck after wide undermining using existing or somewhat larger scar. However, if  tightening of mucles and fat removal is needed to provide desired result, an additional incision underneath the chin may be needed? Only on the basis of in person consultation an experienced surgeon could give you a meaningful opinion. Good luck.

The thyroid incision should not be designed to take excess tension caused by excision of skin.  This would result in scar widening and even thickening.  In addition the scar would have to be wider than usual.  This would not be a good solution.

Thank you for sharing your excellent question.  Although the thyroid removal should not materially impact your neck appearance it is unlikely that any substantial skin improvement could be obtained through the same incision.  In general necks require muscle tightening as a chief issue followed by redraping of the skin, pulled in an outward direction.