The midfielder turned down a permanent move to the Jags in the summer to pen a long-term contract with Dougie Freedman's side before returning north of the border on loan.
After that agreement came to an end at the start of the month, Thistle struck a deal to sign the former Hamilton Accies youngster on a two-and-a-half-year contract.
Fraser made just four appearances for Alan Archibald's side before losing his place in the team and then being hit with a lengthy suspension for an incident in an Under-20 fixture.
He said: "I was just down in Bolton for three days. I knew that Firhill was the place that I wanted to be and I'm delighted to be back. I loved my time on loan here, especially the first four games of the season when I played.
"It's good to get everything sorted. It means that I can concentrate on my football and hopefully get back into the team.
"I'm going to work as hard as I can to get my place in the team and then hopefully keep my place. I've not had a lot of games but I feel fit and I'll be ready to go when I'm asked to play."
After committing his long-term future to Thistle on Friday night, Fraser was handed a place on the bench for the Jags' 3-3 Premiership draw with Ross County at the weekend.
It was to prove another frustrating afternoon at Firhill, with a Lyle Taylor double and Steven Lawless strike not enough to clinch the win in a six-goal thriller.
"Heads were down in the dressing room after the game," Fraser told ptfc.co.uk. "I felt that we deserved to win the game, especially after being 3-1 up. If we had held that lead for a bit longer it might have been a different story but you never know what's going to happen in football.
"The point though does keep us above Ross County and we just need to keep on fighting and look forward to the next game and hopefully win that game. The spirit is good and everyone is fighting together."
After ending their long winless run with victory at Hearts 10 days ago, Thistle should have made it two wins from two games but couldn't hold out against County despite being 3-1 ahead just after the break.
The Jags missed the chance to go level on points with eighth- placed Kilmarnock and boss Archibald knows his side should have held out for victory.
He said: "It feels like a defeat. We have struggled to score goals all season at home but we got three and still didn't win the match. It is hard to take. Last week, we didn't react well when we went ahead and I thought it was the same (on Saturday).
"We panicked when we went 3-1 up. They got the goal back really early and then the worst thing you can do as a defender is start to retreat.
"You move back five yards and it causes you all sorts of problems. I didn't think we defended well as a team. After we scored, we didn't defend as a unit."
Meanwhile, County's Michael Tidser believes his new midfield partner Filip Kiss will only get better and better.
The 23-year-old only moved north from Cardiff on a six-month loan deal last week and former Morton midfielder Tidser, another new recruit after moving north from Rotherham on loan, said: "He scored two quality goals.
"He's not played for almost a year and after 10 minutes he told me he was feeling his calf, so for him to put on a performance like that is incredible. You just wonder what he will be like when he's fully fit."