Muguruza won a hard-fought final 7-5, 6-4 to capture her first Premier Mandatory title and climb to fourth in the world rankings.
It was just the 22-year-old's second WTA title, after she won her first at last year's Hobart International, and made up for the frustration of losing her two previous finals this year, at Wimbledon in July and Wuhan last week.
"For me, to be able to come and win the tournament after losing in the finals of Wuhan last week is a great achievement," she said at the trophy presentation.
"It's amazing, and I can't wait to come back and defend my title next year."
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Muguruza turned 22 a few days ago and became the youngest player to win a title at this level or higher since a 21-year-old Petra Kvitova captured the WTA Finals crown in Istanbul in 2011.
Bacsinszky, twice a winner in Mexico this year, provided Muguruza with a stern test, leading 5-2 in the opening set and 2-0 in the second.
But Muguruza rallied back each time to close out the match in straight sets.
"It's the third time I'm losing against you," Bacsinzky told her conqueror.
"It's tough for me, but it's okay, I'm going to work harder now. Thank you for making me work harder."
Bacsinszky will move into the top 10 when the new rankings are released on Monday and paid tribute to her coach Dimitri Zavialoff, who also used to coach Switzerland's reigning French Open champion Stan Wawrinka.
"I actually want to dedicate this tournament to someone," an emotional Bacsinszky said.
"I came from really, really far away, I almost retired two years ago, and this man over there, my coach, Dimitri, thank you for helping me every day."
(Reporting by Julian Linden in Singapore; editing by Amlan Chakraborty)
