Spain's fifth seed and former world number one Carolina Marin breezed into the final of badminton's Thailand Open Saturday, beating South Korea's An Se-young 21-19, 21-15.

The 27-year-old Spaniard, ranked sixth in the world, is aiming for back-to-back titles in this week's tournament -- the second of three consecutive events in Bangkok that culminate in next week's World Tour Finals.

She came out on top last week against top-seeded Tai Tzu-ying, and continued her winning streak Saturday, maintaining her signature aggressive play against seventh-seeded An.

She spoke of the mental battle of motivating herself just days after being victorious.

"Sometimes it's tough for the mindset when you win a tournament just three days ago and you have to start a tournament all over again," the reigning Olympic champion said after the match.

The pair had already duelled in last week's tournament, with the more experienced Marin winning in a quick 21-18, 21-16 match.

She will face Tai Tzu-ying again in Sunday's finals, who came back after a first-set slump to beat homegrown star Ratchanok Intanon in a 12-21, 21-12, 23-21 nail-biter.

The tense third set was marked by extended rallies before the top-ranked Taiwanese athlete dealt the winning shot against her Thai opponent.

The former world number one clinched a 21-19, 21-15 win to breeze into the final of badminton's Thailand Open
The former world number one clinched a 21-19, 21-15 win to breeze into the final of badminton's Thailand Open BADMINTON ASSOCIATION OF THAILAND / Handout

"In the final moments of the match I just enjoyed playing badminton on court again," said Tai.

"I can say (Marin) is very fast and I'll try to keep up."

The men's singles saw a huge upset when Denmark's third-seeded Anders Antonsen was knocked out of the tournament by his compatriot, Hans-Kristian Vittinghus.

Antonsen had survived a bruising game the day before against India's Sameer Verma, and the impact showed Saturday as he appeared slower in responding to Vittinghus' attacks, who won the game 21-19, 21-8.

"I totally lost hope (by the second game)," admitted Antonsen, who has recovered after contracting coronavirus in December.

The win was unexpected, even for the 42nd-ranked Vittinghus. He had a flight booked back to Denmark on Saturday that he said would now have to be rescheduled.

"I can say that this feels pretty awesome... I'm really looking forward to the final tomorrow," said Vittinghus, who will face fourth-seeded compatriot Viktor Axelsen on Sunday.

The players have been facing off in a spectatorless stadium in Bangkok -- a coronavirus precaution taken by Thailand as part of its biosecure "bubble" to accommodate players who flew in from across the world.

Despite the efforts of tournament officials, four positive cases have been detected so far, forcing an Indian player and an Egyptian player to withdraw.