If after lasik flap is displaced, is it possibe to replace it?

It is not only possible to replace a displaced flap but essential.  If your flap becomes displaced it should be repositioned within 24 hours for best results.

Displaced flaps are very infrequent and can be repaired fairly easily. Be careful to avoid contact sports and rubbing your eyes for a few weeks after the surgery.

if it's within a week postop, this is relatively easy, your surgeon needs to refloat it and replace it, make sure there isn't any epithelium growing under

if over a week it becomes more problematic, often there is epithelial ingrowth which is bad, or striae or wrinkles in the flap which can cause double vision

if you have bad striae, you will need your flap sutured down tight to fix this, and this tight suturing can cause induced astigmatism and poor vision

this is why i switched from LASIK and IntraLase to LASEK and epiLASEK, as the latter are Advanced Surface Ablations that do NOT require ANY cutting or flap, so make your problem IMPOSSIBLE TO HAPPEN IN THE FIRST PLACE

good luck, and go to a very well-qualified surgeon who has completed a CORNEA AND REFRACTIVE FELLOWSHIP if your situation is bad enough to require suturing