The midfielder has penned a two-year deal at Firhill after being told he had no future in Edinburgh by Hibs boss Pat Fenlon.
His move along the M8 brings an end to a long association with the Easter Road club, where he emerged through the fabled youth ranks.
The 22-year-old couldn't make the breakthrough into the first team, however, and with Fenlon set for a major rebuilding of his squad over the summer, Welsh insists he has no regrets about bringing the curtain down on his time with the club.
He said: "I spoke to the gaffer at Hibs and he said that he wanted to take the club in a different direction.
"I didn't see much point in me staying at Hibs to be honest, I never got a chance there so I thought it was probably time to move on and try and better myself somewhere else.
"At the end of the day, I never made the break-through into the first team.
"I did well at youth level for Hibs but I didn't have much luck when I got near the first-team squad through injuries or one thing or the other.
"I felt it was the time for me to move on and give myself a new challenge.
"I need to make sure I am in the team and playing games this year.
"I want to push myself on next season and better myself as a player.
"It is good to have that competition for places, especially going up against two experienced guys in Hugh Murray and David Rowson, but I am sure I can learn from them at the same time. It is good to have that competition in the team.
"I just want to get myself in the team and play as much as I can.
"For the last few years, I have had to train over the summer to get myself ready for the season.
"I'll have a break this year and then I am looking forward to getting back into training ahead of the new season."
Meanwhile, Three lucky Jags fans have the chance to meet Jackie McNamara and his first-team squad by buying a season ticket for the new campaign.
Supporters who purchase their season books this month will be entered into a prize draw, with the winners having their picture taken in the official team photo.
For more information visit www.ptfc.co.uk or call 0871 402 1971.