The 28-year-old, who came through Hibernian's youth ranks, was a free agent after leaving Middlesbrough earlier this year.
Thomson has agreed a deal until the end of the season that will see him paid based on appearances and bonuses.
"Kevin has made the decision that he wants to play here until the end of the season," said Hibernian manager Pat Fenlon.
"That's fantastic and we're delighted. Fitness-wise, he looks fine but he hasn't played much."