The former Hibernian midfielder has penned a contract extension that will see him remain at Firhill until the end of the 2014-15 campaign.
Thistle are back in the top flight this term and have so far secured a draw and a win against Dundee United and Ross County respectively.
Welsh said: "I don't think we could have asked for a better start to the season and the great thing is that the players are really enjoying it.
"The gaffer has done a great job getting so many of last year's squad signed up on lengthy deals and I am glad to have sorted out one for myself.
"He has also added a lot of quality among the new faces so we know that we have to play well to keep our places in the team.
"It is early days but we are pleased with the start that we have made."