The veteran defender weighed in with a vital winner six minutes from the end, allowing Terry Butcher's men to pull further away from relegation.
The Saints looked to get their post-split campaign underway in the right manner after last week's Scottish Cup disappointment at the hands of Rangers.
An early show of dominance, effectively ended by Scott Cuthbert's wayward header, put Inverness on the back foot, but soon Butcher's men pushed out.
Richie Foran's cheeky attempt to head the ball out of Saints' keeper Mark Howard's hands didn't serve as enough of a warning in defence for Gus MacPherson's side.
Then it was too late when Grant Munro met Ian Black's corner from the right to bundle the ball towards goal, with the effort deemed to have sneaked over the line on 12 minutes.
The home side, still to win at their plush new stadium in the SPL, had a couple of half-chances, with Stephen McGinn blazing over and Billy Mehmet failing to find the target with his follow-up header.
It meant Butcher had perhaps the more relaxed half-time team talk, with his side showing more menace going forward.
The visitors started the second half the same way they ended the first with Lionel Djebi-Zadi trying an ambitious one from distance.
Then Dougie Imrie cut inside from the right, not once, but twice, managing to fire over on both occasions in quick succession.
But the blitzkrieg attacks kept coming with Foran's low effort stopped by Howard, followed by another Imrie chance that needed to be saved by Saints' busy keeper.
Despite Thistle's dominance, it was never turned into goals, allowing the Buddies a chance back into the game and they duly got it.
Mehmet's drilled low cross from the right found Jim Hamilton at the near post and he stuck it away to gain parity for the Paisley side.
But it was Tokely that secured victory for Inverness when he put away his second chance six minutes from time after Howard had failed to deal with his first effort.