Barry, the short answer is no, they aren't the same. Thomas Leighton of Dover is not the Thomas Lettyne (Laighton, Layton, Laughton) of Lynn, Mass. (b. about 1612, d. Aug. 8, 1697) who was on the list of freemen in 1639. I made a guess and at the first try I found him in WikiTree already, under the name Thomas Laughton (Laughton-85) only the profile doesn't seem to know much about him. His descendants were Laughtons. You can probably find him in:
Charles Evans Banks, Planters of the Commonwealth
Charles Pope, Pioneers of Massachusetts
Charles Evans Banks, Topographical Dictionary
John Savage, Genealogical Dictionary of New England
Sorry I didn't keep the page numbers.
I hope that helped.