Defending champion Daniela time winner Vera Zvonareva was forced to retire from her match because of a hip injury.
Hantuchova, this year's third seed, battled past Vania King, 7-6 (9-7), 6-4, giving the Slovakian a 7-0 career mark against the American. The two also met earlier this year in the second round of the Australian Open tuneup in Brisbane.
Mirza was the 2009 Pattaya runner-up, losing to Zvonareva in the final. The top-seeded Russian also won this title in 2010. Friday's quarterfinal against Romanian Sorana Cirstea was all even when Zvonareva called it quits.
Cirstea, who reached the quarterfinals earlier this season in Hobart, took the first set on Friday, 6-2, before Zvonareva captured the second, 6-4. It was 2-2 in the third when the two-time Grand Slam runner-up decided she could not continue.
The seventh-seeded Cirstea will next play another Russian in the semifinals, as fourth-seeded Maria Kirilenko earned a spot in the final four with a 7-6 (7-2), 6-1 victory over Thai crowd favorite Tamarine Tanasugarn. Tanasugarn has been a runner-up at this event twice, first back in 1996 and again last year.
Kirilenko, a third-round loser to Petra Kvitova at the Australian Open, hasn't won a WTA crown since 2008.
The 2012 champion will collect $37,000.