It surely wasn't a high-ranking soldier or official, it would not be one that was a favorite or popular among the troops. This speculatively unfortunate person was possibly one who was the least liked. Maybe it was the one that got in trouble and is on some sort of probation period, or maybe it was a prisoner whom they most disliked and picked on. Possibly a child, snatched from the street was chosen to do the prickly deed...probably not, the bible tells us the soldiers weaved it. I find it hard to imagine that the unlucky person picked for the creation of the crown of thorns was a person ready and willing to do such a chore. Surely his hands and arms were pretty torn up in the process of gathering, cutting and weaving the thorny branches and placing it onto our Lord's sacred forehead. I just imagine.
In the pictures depicting the placing, rather, thrusting of the thorn crown on Christ's suffering head, I do not recall bloody hands of the soldier....just the newly released streams from our Lord. There seems to not be an interest in the pain that was inflicted upon the unfortunate soldier who created this crown. But thinking about the reality of dealing with thorny bushes, one cannot escape a scratch or two, if not a puncture. Believe it or not, the crown of thorns was not officially part of the torture, it was meant as a piece of mockery as the soldiers spat and flogged Christ as “King of the Jews” The explanation in my NAB bible in Matthew 27:29 says, "probably of long thorns that stood upright so that it resembled the "radiant" crown, a diadem with spikes worn by Hellenistic kings. The soldiers' purpose was mockery, not torture." Well, still in all, why not make one of soft leafy branches or at least just plain reeds weaved that didn't add to the heinous treatment of our Lord?
No one knows, no one will ever know, except perhaps, the soldier.