The Buddies had not tasted victory on home soil since defeating Ross County by the same scoreline back in May but halted a run of 14 games without a win, six short of Falkirk’s top-flight Scottish record, in Paisley through Thompson.
The first meaningful effort came from home debutant Alan Gow, who picked the ball up 30 yards from goal and made Michael McGovern work for the first time in the Accies goal.
A succession of corners then almost brought the home side the lead. First, James Dayton’s in-swinging ball was cleared back out to the winger’s feet, and his second cross picked out the head of debutant centre-half Victor Genev, whose header looked to be creeping into the top corner before a fine diving intervention by McGovern.
Gow then tested McGovern again, showing good feet on the edge of the area to evade two challenges before trying a looping effort which the Accies No 1 did well to tip over.
Hamilton almost grabbed a shock lead lead when some splendid, intricate passing ended in a one-two on the edge of the area between Jason Scotland and Ali Crawford that saw the former drag his low right-foot effort just wide when unmarked.
Jason Naismith then whipped in a fine delivery at the other end that caused a moment of alarm for Martin Canning, the ball slicing off the player-manager’s shin and over the bar
Canning should have done much better at the opposite end soon after when Crawford’s free-kick from halfway found him unmarked inside the St Mirren area, but he seemed to lose his bearings and headed well wide.
The St Mirren fans were screaming for a penalty at the start of the second half as Thompson claimed he was being pulled in the area by Ziggy Gordon, but referee Crawford Allan waved away their appeals.
Thompson then created a great chance for the home side when he drifted wide before turning and floating a delightful ball into the path of John McGinn, the midfielder meeting the ball with his head as it bounced up off the slick surface and drawing a wonderful point-blank save from McGovern.
They were not to be denied for long though, and after 62 minutes Thompson put St Mirren in front.
Kieran Sadlier, who came off the bench for his debut at half-time, did well to drive inside before spreading the ball to Dayton on the opposite wing. Dayton drove past the challenge of Kieran MacDonald before clipping a lovely ball into the front post where Thompson volleyed beyond McGovern for his first league goal of an injury-hit season.
Hamilton could have equalised almost immediately and again it was Canning who had a headed opportunity, getting a run on the St Mirren defence to meet Darian MacKinnon’s lofted cross but heading straight at Marc Ridgers.
Losing the goal seemed to belatedly bring Hamilton to life and Crawford had a good chance after riding a weak challenge on the edge of the box, but fired over from a narrow angle.
Canning then had his best opportunity of the match, when a free-kick wide on the right was beautifully clipped in by Crawford on to the head of the Hamilton boss, but he could only send his effort skidding wide of the right-hand post.