Substitute Madelen Janogy then scored a fine individual strike - her second global goal - in the fifth minute of stoppage time to wrap up all three points. Morgan scored her fourth on an easy shot from the middle of the box after Rapinoe weaved through the left side of the Thailand defense.
"You want your forwards hot in a tournament and it's a great start especially for Morgan". Morgan put her arm around an opponent, who was wiping away tears on the pitch moments after the final whistle.
According to the Federation Internationale de Football Association ranking board, as of Tuesday, the USA was ranked as the number one team in the tournament, followed by Germany, England and France. A trio of Americans swarmed Thailand keeper Sukanya Chor Charoenying, and a moment later, Alex Morgan scored a goal with her head.
They'll next face Chile on Sunday, June 16 and Sweden on June 20, before the knockout stages begin on Saturday, June 22.
"Every goal matters in this tournament and so that's what we were working on this game."Even then, though, Thailand held reigning champion Germany to just four goals.
But some pundits have criticised the American players for both their ruthlessness in dishing out such a defeat, and excessive celebrations late in the game as the goals piled up.
World Cup favourite the U.S. has thrashed Thailand 13-0 to lay a marker down to the rest of the competition in its opening match in Riems, north-east France.
The USA's previous biggest victory at the World Cup came in 1991, when it beat Chinese Taipei 7-0. "You're going up against a team that's first time in the World Cup, they're just happy to be there".More news: The next Legend of Zelda is in development
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The Americans' 13 goals set a new record for the most goals in a single World Cup match.
"It's incredible, I don't know, I'm speechless", Morgan said.
Thailand was never a real threat to the US national team. But her performance against Thailand proved that she will be the one the Americans rely on when it comes to defending their title.
A set piece led to the third goal for the USA just past 30 minutes, as Lindsey Horan hit her close-range shot into the roof of the net.
Sauerbrunn, at her third World Cup, was a steadying force for the US defense in Canada when the USA went 540 minutes without conceding a goal. From there, she really laid it on in the second half.
Wambach, 39, added: "With all due respect: did you see @alexmorgan13 last two goals and her last assist?!" Now, Morgan has eight career World Cup goals.
Sweden beat Chile in the other game in that group.
Samantha Mewis opened the floodgates five minutes after the break as the US made life miserable for the Thais by regularly finding the back of the net.
Ahead of Tuesday's match, sports prognosticators had predicted that the US, as the defending tournament champions, would overwhelmingly defeat Thailand, according to USA Today. The American's pass accuracy was at 82% and Thailand only reached 61%.