Stewart Sifakis [known for errors] writes in his Compendium of the Confederate Armies - Florida & Arkansas - page 121:

Arkansas 46th Infantry Regiment Mounted
Organized: late 1864. Surrendered by Brig Gen M. Jeff. Thompson, commanding, Army of Northern Sub-district of Arkansas, District of Alabama and West Louisiana, Trans-Mississippi Department, on May 11, 1865.
First Commander: W.O.Coleman [Colonel]
Assignments: Unattached - Shelby's Cavalry Division, District of Arkansas, Trans-Mississippi Department [August-September 1864]
Unattached - Shelby's Cavalry Division,Army of Missouri, Trans-Mississippi Department [September-December 1864]
Northern Sub-district of Arkansas, District of Arkansas, Trans-Mississippi Department [April 1865]
Northern Sub-district of Arkansas, District of Arkansas and West Louisiana, Trans-Mississippi Department [April-May 1865]
Battle: Price's Missouri Raid [September-October 1864]