Thailand's Ratchanok Intanon downs Indian star PV Sindhu

Former world number one Ratchanok Intanon landed a crucial victory over Indian star PV Sindhu at badminton's World Tour Finals in Bangkok on Thursday.

It was a double victory for Thailand's hopes, as 13th-seed Pornpawee Chochuwong also booked a semi-final spot after a shock win over Taiwanese top-ranked Tai Tzu-ying.

Intanon trailed for most of the first game against Sindhu, but showed a ballerina's footwork and killer instinct to take it 21-18.

The 25-year-old Thai claimed the match taking the second game 21-13.

"I just want to keep going and focus on winning, point-by-point," Intanon said afterwards.

"It wasn’t my day," said Sindhu.

"Losing the first game made the difference. My timing was a bit off, so a bit disappointed."

Both players were coming off an initial loss in the round-robin tournament; Tai beat Sindhu, the Rio Olympics silver medallist, in a three-game thriller on Wednesday.

Chochuwong upset fifth seed Intanon in three games on Wednesday.

On Thursday, Chochuwong, 22, went into her match having never won a game against Tai in previous encounters, but won 21-17, 21-11 in 37 minutes.

Earlier, Carolina Marin -- looking for a hat-trick of titles -- marched towards a swift victory over Canada's tenth-ranked Michelle Li 21-16, 21-13.

"I think I keep getting better and better," Marin said.

In the men's singles, Taiwan's 12th-ranked Wang Tzu-wei was victorious over India's 14th-seed Srikanth Kidambi in a three-game match that lasted 78 minutes, finishing 19-21, 21-9, 21-19.

The delayed 2020 season finale is the third tournament behind closed doors in three weeks in Bangkok, as badminton resumes after months of coronavirus cancellations.

The top eight players in all singles and doubles disciplines are contesting this week's tournament, but China and Japan are absent because of coronavirus problems.

Despite the strict biosecurity arrangements, four people inside the tournament "bubble" have tested positive, including two players who were forced to withdraw.