Bacsinszky, who recently returned from a six-month injury lay-off, looked to be feeling the effects of her quarter-final victory over Aryna Sabalenka.
That success ended the Belarussian's hopes of making the WTA Finals, but Pliskova, who holds the eighth qualifying spot, is firmly on course to feature in Singapore and will now face Caroline Garcia in the final.
"I felt good," the No.1 seed said after a win that stretches her advantage over nearest rival Kiki Bertens.
"I quite like her [Bacsinszky's] game, and I just had the match under control. I know she can play better than she played, but I was just worried about myself.
"It was pretty fast today — but she was a little bit tired because she had a long match yesterday."
No.2 seed Garcia overcame Hsieh Su-wei 6-3 6-4 to reach her first final of 2018.