Pliskova, who advanced from her group for the second straight year, beat Kvitova 6-3, 6-4 to improve her record to 2-1 at the season-ending tournament.
At the Australian Open and the French Open, players still have to win by two games in the final set in singles matches.
Umpire Ramos gave Williams a code violation after her coach gestured in her direction early in the second set of Naomi Osaka's 6-2, 6-4 victory over the American.
Halep's withdrawal means Kiki Bertens has qualified for the final spot, joining Angelique Kerber, Naomi Osaka and many others.
The 27-year-old Halep had her best year on tour in 2018, reaching the Australian Open final and then winning her first Grand Slam title a few months later at Roland Garros.
Serbia's Novak Djokovic climbed one spot up to the second, after claiming the Shanghai Masters title for the fourth time in a row on Sunday.
Djokovic holds an 11-0 overall record in finals played in China, where he also won the Beijing tournament six times and the 2008 year-end Tennis Masters Cup.
Paes, who is ranked 69, added 110 ranking points to his kitty and shared a prize purse of USD 7750 with his partner.
Coric earned passage to the final by taking down the top-seeded Federer 6-4, 6-4 in the semifinals on Saturday.
Leander Paes is one win away from winning his second title of the season on the Challenger circuit, reaching the final of the Santo Domingo Open.
Roger Federer reached the semi-finals on Friday by beating eighth-seeded Kei Nishikori 6-4, 7-6 (4). His first two matches both went three sets.
Federer, the defending champion, beat Daniil Medvedev 6-4, 4-6, 6-4 in the second round despite being broken late in the second set.
Djokovic's second-round victory improved his perfect record against the 41st-ranked Chardy to 12-0 in matches played, and 28-0 in sets won.
Wozniacki said eight was her lucky number and, having won in Beijing eight years ago, she "felt it was my year."
Daniil Medvedev beat local favorite Kei Nishikori 6-2, 6-4 in the Japan Open final on Sunday for his third career ATP title.
Halep lost the first set 6-1 to Tunisia's Ons Jabeur before retiring with a back injury that she also had problems with at last week's Wuhan Open.
Halep lost the first set 6-1 to Tunisia's Ons Jabeur before retiring with a back injury that she also had problems with at last week's Wuhan Open.
Roger Federer earlier put Team Europe ahead by saving three match points for a 6-7, 7-6, (10-7) victory over John Isner.
Pliskova broke Osaka for a second time to go up 5-4 in the second set and then hammered her sixth ace to secure her 11th career title.
India are currently on top with four golds, five silvers and a bronze medal in the competition.
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