Thistle slumped to a fifth consecutive league defeat last Saturday as their loss of form continued.
Once again Thistle were forced to give up home advantage as the ongoing issues continued with their home pitch continued.
With just over a minute on the clock St Monans took the lead when a slack pass from Moir put Gough under as he sliced a hurried clearance into the path of Redpath who dispatched the ball into the top corner.
With 12 minutes gone the Swallows doubled their advantage when Anderson spilled a low shot and Jardine reacted fastest.
Just before the break St Monans all but killed the game off with a killer third after Anderson initially pulled off a good save only for the ball to cannon off Thomson and into the path of Jardine who made no mistake.
Any hopes of an unlikely comeback were killed off just nine minutes after the restart when Thistle conceded tamely from a corner with Horsburgh providing the finish for the inform Swallows.
Worse could have followed just two minutes later when Carson gifted a penalty with a clumsy challenge however Anderson produced a great save from Low.
Thistle continued to work away and probably enjoyed their best spell of the game in the last 20 minutes and deservedly pulled a goal back minutes from time through an excellent individual goal from Foulkes but it was scant consolation for Thistle who have slipped into a potential relegation battle.
Alba Mortgage Solutions man of the match – Dan McArthur.
Team – Anderson (Henderson 75), Carson, Thomson, Gorgon (Ireland 46), Gough (Foulkes 59), Shepherd, McArthur, Moir (Palacios 63), Jukes (Cameron 59), Barnes, Petrie
On Saturday Thistle face local rivals St Andrews University in the league.