This is the place to go to get the lowdown: http://www.longdistancevoter.org/arkansas
You can vote by absentee ballot in Arkansas if you fall into one of the following categories:
-you will be unavoidably absent from your polling site on election day, OR
-you will be unable to attend your polling site on election day due to illness or physical disability, OR
-you are a member of the U.S. armed forces, merchant marines or the spouse or a dependant family member, OR
-a U.S. citizen domiciled in Arkansas but temporarily living outside the territorial limits of the United States.