Ko said after her victory that she put any thoughts of winning the $1m Race to the CME Globe well into the back of her mind.
"I didn't really think about it. Even playing out there today I just set myself the goal to make myself as many birdies and just go out there and have fun. At the end of the day it's been like this [playing a playoff] - I thought I'd be playing 72 holes but I've played a round of 76.
"I'm excited that the season is over but it's been great."
The victory is Ko's third of the year and caps off a remarkable maiden season on the LPGA Tour after earlier this month becoming the youngest player to win the rookie of the year award. Along with three titles the teenager has had two runner-up finishes and nine additional top 10s.
The only thing she didn't tick off this year was a major tournament win, finishing third at the LPGA Championship and eighth at The Evian Championship.
"This has been a big year, a roller-coaster ride. I've learnt so much this year, like these kind of playoffs - my first as a professional. I've been learning a lot. I think next year's going to be a fun year."
Ko said one of the first things she'll be purchasing would be a four-figure bag for her mother.
"I would have got it for her anyway, she really deserves it and I wouldn't be here without her," Ko said.
Ko began the season finale in third place on the Race to the CME Globe standings behind Stacey Lewis and Inbee Park. However the world number one and two both faded over the final two rounds while Ko took control the lead.
The New Zealanders sat in fifth going into the final round but took the outright lead with birdies at holes 4, 6 and 8 to be nine-under at the turn. She stretched her lead to two shots over Germany's Sandra Gal and Spain's Carlota Ciganda with a fourth birdie of the day at the par four 13.
However Ciganda and Paraguay's Julieta Granada tied Ko for the lead with four holes to play as all three players missed chances to take the outright lead down the stretch.
Ko closed with a four-under 68 for the second straight day to finish at 10-under with the clubhouse lead before Granada and Ciganda joined her in a playoff.
After all three recorded pars on the first playoff hole, Granada missed a short putt on the second trip down the 18th to leave Ko and Ciganda fighting for the title.
Ciganda's wild second shot on the fourth playoff hole forced her to take a drop, handing the title to Ko.
