Funny, I have the same query. My house is 10 years old. I just replaced a section of the floor where there was a water leak. The vinyl is back on, but there are some really brutal seam lines. I want to know if I can put a thin set concrete down over the vinyl then a laminate floor. Any advice would be welcome! Thanks!
You don't need thinset under laminate, just use a top quality acoustic pad and float the floor over the existing vinyl removing any raised edges. Consider moisture potential in choosing the floor. Thinsets are used under cermaic tile. If you are laying ceramic, attach 1/4 inch cement board then use the thinset to attach tiles.