Thomas served in Company K, 10th Alabama Infantry, not the 18th. The General Order should provide the information as to the charge/s against him, I doubt it would provide the results. His records do not record his death, but we do see that he had clothing issued the 2nd quarter of 1864.

I would suspect that this G. O. would be found in the National Archives. However, as I understand it, these records are no longer available to the general public, Washington, DC.

There are persons who will research these records for a fee. I posted recently the name of a lady, retired NA, who will perform these services.
Perhaps someone will see this and come up with her name and address.

The court martial record card refers to General Order No. 5-18, Department of N. Va [Northern Virginia] - Lee, January 19, 1864. It is important that you provide the Headquarters ID.