The only Samuel French I see listed in the Nat Park Service ( http://www.itd.nps.gov/cwss/soldiers.cfm
), in a NY regiment, that served in Louisiana was in the 75th NY Infantry. This regiment was "Organized at Auburn, NY, and mustered in November 26, 1861." According to their information, the regiment, at the time he died, was on "Duty in the District of LaFourche till February, 1863. Expedition to Bayou Teche January 12-15. Bayou Teche January 13. Steamer "Cotton" January 14." The next location shown was Port Hudson in March, after his death.
There is an interesting article at http://www.sonofthesouth.net/leefoundation/civil-war/1863/february/battle-bayou-teche.htm , that describes the Battle on the Teche on the 14th of January and touches on the part of the 75th NY. If this was your ancestor he may have been wounded here and died later.