Ok Tim, here is my best explanation for you...

My paternal GGF was John Harmon Holcomb, an assistant surgeon with the 23rd
Arkansas Regiment, company H, recruited out of Clark County. He participated
at the 2nd Battle of Corinth and Hatchie bridge and then at the siege of Port
Hudson. He was paroled but unclear as to exactly where he went after this

At Port Hudson, the 23rd Ark was consolidated with the 14th, 16th, 17th, 18th and 1st Ark Inf Battalion under Col Crockett of the 18th.
All of the enlisted were paroled, perhaps because he was a doctor they paroled him as well, and they were returned across the Miss River. Once paroled, Dockery began building what he planned to be a mounted force of a consolidated group of many of these parolees of the 12th Sharpshooters, 15th, 18th, 19th, and 20th Ark and possibly some of the 12th Infantry. Colonel Lyles of the 23rd took the men who lived north of Ark river in NE Ark, and mounted them as Lyle's regiment and assigned eventually for Missouri Raid to Fagan's division. But those in south Ark under Dockery were all stationed at Monticello but not enough good horse flesh to mount everyone. These men were 15th, 18th, 19th, Rapley's 12th Sharpshooters and mixture of men from 12th Inf as well as 23rd Inf. The mounted portion fought at Mt Elba during initial stages of Camden expedition and became part of Fagan's Cavalry Division seeing action in Camden expedition. The dismounted portion became what was known as H.G.P. Williams regiment aka Docker's Dismounted Casuals. They fought at Jenkins Ferry on north side of Cox Creek...I have an Austrian Lorenze rifle recovered from that area.

It is possible that he was assigned to another unit and participated in the Camden Expedition with
Dockery's Brigade. As a surgeon he would be in demand. (He had resided south
of Camden in the 1850's but by 1860 was living in extreme southern Clark
County.) I saw some information that some of the prisoners taken in the
Longview/Mt Elba skirmish were from the 23rd, indicating at least some of his
unit were with Dockery. I have not found any information to confirm his
whereabouts but do believe he remained in camp in south Arkansas and did not
just return home after his parole from Port Hudson.

Yes this all fits in with what I mentioned above. A number of PH parolees became part of the forces in Arkansas. By September 1864, the under-strength commands consisting of the Eighth Arkansas Infantry Battalion, Twelfth Arkansas Infantry Battalion, Eighteenth Arkansas Infantry, and Twenty-Third Arkansas Infantry were consolidated to form the Second Arkansas Consolidated Infantry under command of Colonel Thomas J. Reid Jr. Placed in McNair’s Arkansas Brigade of Churchill’s Division, 2nd Army Corps of the Army of the Trans-Mississippi, the remnant of the regiment saw no fighting for the remainder of the war. The final months of the war were spent garrisoning posts across south Arkansas at Monticello and Camden as well as Minden, Louisiana, before relocating to Marshall, Texas, in April 1865. Hope this helps explain what may have been going on with him.

Now as to the 1st Ark Inf US, they did indeed participate in those rear guard defenses and skirmishes before they moved in to Camden. At Jenkins Ferry they participated most likely on the Union left flank defending against the Missourian's and later Texan's assaults. I personally have found Thayer's camp on his way down to link up with Steele through contemporary writings. And afterwards they would return to Fort Smith eventually. I think they went to LR and then probably took boats up river but I would have to research it to make sure.

Hope this answers some of your questions.