Kirby Smith surrendered the Trans-Mississippi Department on May 26, 1865 under the same conditions afforded the other capitulating generals. The soldiers were parolled and allowed to return to their homes in peace so long as they abided by their paroles.
The People were allowed to go home.
Actually, he didn't sign the articles until June 2nd. The 26th was the date of the Union officers' interview and negotiation with Kirby Smith's and Canby's representatives. In Kirby Smith's case, his representative was Gen. Simon Buckner.
I'm looking for my source (it isn't Fehrenbach), but the main Confederate encampment in Texas, east of Houston, didn't break up until a day or two after Gordon Granger showed up in Galveston on June 19th and started running his mouth nonstop about illegality, null and void, and blah, blah, blah.
The Confederate troops didn't just disappear because Edmund Kirby Smith inked a document and pointed his horse toward Mexico. What did disappear was much of the Confederate chain of command and Confederalized Texas troops' legal basis for resistance to the 25,000 men Phil Sheridan was leading by sea from City Point, Virginia en route Texas to reinforce Granger in Galveston and the small garrison (reduced by the battle at Palmito Ranch on May 13 -- correction to date) at the mouth of the Rio Grande.
The State of Texas never signed a surrender document, and so perforce neither did its People in arms as the Militia. Of course, if Texas did surrender, you're free to produce the surrender document, it'll be a useful addition to the discussion. I would encourage you to spend as much time as possible looking for it.
But Kirby Smith's instructions came from the Confederate governors of Arkansas, Louisiana, and Mississippi, not from Texas.
One last note: the last reference to fighting (on land, anyway) that I can find is to a skirmish that took place near Rocheport, Missouri, on May 24, 1865, between federal troops and Confederate irregulars.
Kirby-Smith had NO army to surrender. They had already gone home. I can quote you some sources on this if you like.