Thiem came out swinging and made the perfect start, breaking in the opening game after Sock dumped a forehand into the tape.
Sock made good use of the drop shot early on to get himself on the board at but struggled to make inroads on the Austrian’s own deal.
Thiem moved further in front after another unforced error from the Sock backhand to go up a double break at 4-1.
The recently-crowned US Open champion wrapped up the first set in less than 30 minutes, with Sock lunging for a forehand but missing into the net, as the American was broken for a third time.
Both players held serve comfortably to kick off the second stanza, with Sock sealing the second game of the set with a perfectly weighted lob that sent Thiem scrambling.
Sock had a sniff of a break at 0-30 in the third, but Thiem fought back to edge in front, with Sock complaining about the court surface to the umpire.
Both players continued to dominate behind their serve, with Sock demonstrating an increasing desire to come forward and finish points at the net as he squared things up at 3-3 with a delightful forehand drop shot.
Sock’s serve came under serious threat in the eighth game, and Thiem eventually broke through the American’s defenses after a Sock forehand clipped the tape and flew wide on the Austrian’s third break point, leaving Thiem to serve for the set at 5-3.
Thiem again found himself down at 0-30 on serve, but fought back and produced a sublime drop shot to create a set point, which Sock saved with a blistering forehand which Thiem could not control.
The third seed sealed the second set at the second time of asking with a deft forehand volley to take a commanding lead in the match.
Sock’s third double fault cost him his serve early on, and despite his remonstrations with the umpire about the ball mark, he found himself with a mountain to climb down two sets and a break at 1-2.
However, the American showed true fighting spirit to break back immediately with a clean backhand return down the line which Thiem could only watch sail past.
Sock carved out an opportunity to break at 3-2 but Thiem snuffed it out with a delicate drop shot of his own and went on to level up at 3-3.
Thiem made the breakthrough in the following game, forcing the forehand error from his opponent to move up 4-3, two games from victory.
Much to his credit, Sock continued to battle and was rewarded for his efforts after another fantastic backhand return which caught Thiem off-guard, to break back for 4-4.
After consecutive holds from both, the set was decided on a tie-break. Sock surrendered leads at 4-2 and 6-3 to hand Thiem victory, with a backhand sprayed wide the final blow for Sock, who fought admirably but was unable to match Thiem’s level on court Suzanne Lenglen.
Thiem goes on to face either Norwegian Casper Ruud or Tommy Paul of the USA. Ruud, who has been in good form of late, reached back-to-back semi-finals on clay at the Rome Masters and also the event in Hamburg last week. Paul, meanwhile, is enjoying his best run at Roland Garros.