Thiem stayed with Nadal in the early going on a cloudy and steamy afternoon; the temperature was 77 degrees (24 Celsius), the humidity approached 70 per cent.
In 11 finals in Paris, Nadal has only lost six sets as he matched the all-time record of most singles titles won at the same Grand Slam event set by Margaret Court at the Australian Open during the 1960s and 70s.
But at 4-5 Thiem's serve let him down badly, handing Nadal three set points.
Nadal celebrated in relatively low key fashion, but then there is not much novelty value in this. He saved two of a mere three break points. Thiem withstood a barrage of break points to hold in a marathon sixth game, which he thought he had won at 40-30 when he left a wide ball, only for the umpire to overrule the line judge. So there was mild concern when Nadal called for the trainer midway through a game, requiring treatment on what looked like cramp in his hand. But against an opponent of Nadal's caliber, a lack of variance in his game plan proved crippling. Nadal had another massage at 5-2 and he ended Thiem's ordeal on his fifth match point when the Austrian returned long.
Trump invites National Hockey League champ Capitals to White House but not NBA winners
Championship players have in recent years snubbed both Trump and President Barack Obama by declining White House invitations. Curry is referencing last year's controversy when the Warriors declined an invitation the White House.
But against Thiem, there was nothing wrong with Nadal's start.
The top-seeded Nadal enters Sunday with a 10-0 record in title matches at Roland Garros and an overall career mark of 85-2 at the clay-court Grand Slam tournament.
Dominic Thiem couldn't get near the veteran on the day, despite the fact the Austrian had been the only player to defeat Nadal on Clay during this current season.
F1 Raceweek: Hamilton seeks to match Schumacher - Canadian Grand Prix in numbers
Bottas played down the delay to the new engine, saying it would have been only "a small gain compared to the old one" anyway. Mercedes are leading both championships after six races, with Lewis Hamilton 14 points clear of Ferrari's Sebastian Vettel .
Nadal's Barcelona Open semifinal win over David Goffin was his 400th tour-level clay-court match win, making him the fourth man in the Open Era to win 400 matches on clay, after Vilas (659), Manuel Orantes (502) and Muster (422).
The forecast says there is a chance of rain.
That was swatted away with Nadal's double-handed backhand, though, and the second set duly went the way of the favourite.
No evidence of any foul play in Bourdain death, prosecutor says
And makes me very sad for him to have - to have a succumbed to that", he shared. "My love & prayers are also [with] his family, friends and loved ones".