According to Booth's Records (which list most soldiers from Louisiana) there are two Louis Deville's that fought in the war. Here are there names and units:

Deville, Louis, Pvt. Capt. Todd's Indpt. Co. (Prairie Rangers) La. Cav. En. Aug. 21st, 1862.
Opelousas. La., for the war. Present on Roll to Dec. 31st, 1862.

Deville, Louis, Pvt. Co. A. 28th (Thomas') Regt. La. Infty. En. April 6th, 1862, Opelousas, La.
Present on Rolls to Feb., 1863. Federal Rolls of Prisoners of War show him captured and paroled
at Vicksburg, Miss., July 4th, 1863.

Please note that both are from Opelousas, La -

There is a listing of buriel places for La Soldiers - I can't seem to find the address right now. This might help you narrow down which one it is.

You may wish to review the 1860 US Census to get informatoin on the man's family, if married, etc. There should be a microfilm at the state archives in Baton Rouge, perhaps even in the local library, if it a LARGE one.

Hope this helps in the mean time.

JIMT