For a Double Eyelid Revision, Need to Remove Previous Sutures?

For a revision, I would recommend an open technique.  In this case, if the sutures were still present, then I would remove them as part of the operation to change the lid crease.  There would be no productive reason to leave them in.

You can increase the height and style of your double eyelid after Non Incision Asian Blepharoplasty.  In this case you wouldn't absolutely need to remove the sutures that were there before.  But removing them would not be very difficult and shouldn't markedly impact your procedure if it were redone in an open fashion.  You can also do the revision with the non incision technique and it should be done just like if your current fold is natural and not from surgery. 

I prefer doing Asian Blepharoplasty in an open fashion because I think it is more accurate and leads to more reliable results.  I don't know how long you had this procedure but it might have lasted longer had your done the double eyelid procedure in an open manner.  To make the crease lower would be much more difficult open and closed.  It is not really possible even to make it lower in a closed non incision technique.