What is the White Visible Through my Tummy Tuck Incision?

It sounds that you have some issues from wound healing after tummy tuck. The white stuff you see is likely what we can fibrinous exudate, or simply some non viable areas of the skin and the protein that the cell excrete.
I would talk to your surgeon and see what he would like to do for it. I usually place a stitch on either side to prevent the incision from opening up further and treat the area with dressing changes and allow it to heal on its own.

Good luck.

Hello,
If you said you saw a "white thread," I'd say it was one of the sutures maybe. If it is just white tissue, it is likely part of the healing process. Have your surgeon look just to be sure, but I think you are probably fine here.
Best Regards