Thai teenager Ratchanok Intanon took the women's singles title at the badminton world championships in Guangzhou Sunday, beating Olympic champion Li Xuerui 22-20, 18-21, 21-14 in a massive upset.

Ratchanok, 18, becomes the first ever Thai player to win gold at the world championships after defeating 22-year-old top seed Li, who was gunning for her first world title.

The three-game thriller was a battle of technical skill and stamina, with Ratchanok pushing a more experienced Li around the court with a sophisticated repertoire of shots.

Ratchanok came back from 19-12 down in the first game to clinch it by two points, with a grim-faced Li fighting back to take the second.

But the supremely relaxed Thai looked physically and mentally stronger in the final game, holding on to a lead as Li threw everything at her.

At the end of the match Ratchanok dropped to her knees in tears on court before bowing to an applauding stadium.

A smiling Ratchanok, who still has braces on her teeth, said she would meet Thailand's Queen Sirikit on Monday, which is a national holiday to mark the queen's birthday and Mother's Day.

"I am going to bring my victory to the queen and to my mother and godmother as a gift," Ratchanok said.

"Before this match I didn't have confidence when I was competing against the top players, but after today I will.

"Li was not playing like herself. I felt really relaxed and I think she was nervous. I have played her five times and she has won four, so it was amazing that I beat her today."

It was a fairytale moment in a career that started when she was five years old and her parents were working in a dessert factory, taking Ratchanok with them each day.

Ratchanok and other children were sent to a badminton academy by the factory owner, who felt it was dangerous for them to be there.

The teenager supports her family through her badminton career.

"Being the champion has been my dream," she said. "At the end of the match all the tough moments from all the years came into my mind and I thought, 'Finally, I got it.'"

Speaking after the match a deflated Li said she had found it hard to concentrate.

"It wasn't being the top seed that affected my mindset -- I think I was just too eager to win.

"We prepared thoroughly for the match, but it was hard to implement the plan. When I tried to execute my strategies, I would make errors.

"My opponent played very well and seemed very relaxed, which put a lot of pressure on me."

Reigning women's doubles champions Wang Xiaoli and Yu Yang had started the day well for China, taking the title with a 21-14, 18-21, 21-8 win against Koreans Eom Hye-Won and Jang Ye-Na.

With Li then beaten by Ratchanok, home fans were looking to energetic Chinese mixed doubles pair Xu Chen and Ma Jin to take the next gold.

But it wasn't to be as third-ranked Indonesian duo Tontowi Ahmad and Liliyana Natsir fought back from behind in the third game to defeat the top seeds 21-13, 16-21, 22-20 in a nailbiting finish.

Natsir becomes the only mixed doubles player ever to have won three world championship gold medals.

Indonesia were celebrating again after men's doubles pair Mohammad Ahsan and Hendra Setiawan beat Mathias Boe and Carsten Mogensen of Denmark in two sets 21-13, 23-21.