Linette, a semifinalist in Thailand last year, had dropped just one set heading into the final and she produced another dominant display in Hua Hin to win her second WTA title.
The Pole pounced on Kung's second serve and used her variety to dominate the 19-year-old, whose inexperience showed in her maiden WTA final.
"It was so tough today, I had to keep it together to the very end," said Linette, who won her first WTA title last year at the Bronx Open.
"I knew I need to be the one leading the game. I knew I have to be really aggressive and I had that confidence from the matches before, and I'm really glad that I managed to do what we planned with my coach."
It was still a good week for Kung in only her second main-draw appearance at a WTA event.
"I'm just trying to build up my ranking even more and play day by day, and just have fun and enjoy on court," the teenager said.
Linette's victory saw her enter the top 40 in the WTA rankings for the first time.