The win is the third for Hantuchova in Pattaya, who took back-to-back titles in 2011 and 2012.
But it was far from plain sailing against a 21-year-old Croatian rival who was ranked five places above her, enjoys a ten-year age difference and took the first set 3-6.
With an early lead in the second, Tomljanovic appeared on course for a breakthrough tour win.
But a dogged Hantuchova refused to give in, clawing her way back into the game to take the set 6-3.
Both women had endured punishing three-set semi-finals on Saturday, with baseliner Hantuchova prevailing over New Zealand’s Marina Erakovic, while Tomjanovic took nearly three hours to vanquish seventh-seeded Monica Puig.
The pair were again forced to slug it out in a tight third set that saw the right-handed Croat break back after dropping serve early on.
The pair then traded games as the match crept towards the two-hour mark, before another Hantuchova break saw her seal victory 6-4.
The 73rd-ranked Hantuchova recently changed coaches, taking on former Li Na and Justine Henine mentor Carlos Rodriguez.