Frigidaire Dryer GLER642AS3 drum off balance problem...It dries but it's making a thumping noise, I think the drum is off balance.

It is not the drum making the thumping noise it is your drum rollers that flat spots on them.
----------------------------------------------------------------------------------------------------------------------------------ALWAYS UNPLUG YOUR DRYER BEFORE STARTING ANY REPAIRS
Your problem sounds like drum rollers have flat spots on them or in need of lubrication, or maybe your drum belt has slipped off of the idler arm pulley.
If you have a front loading machine,

Remove the electrical console that holds the timer switch, start switch, etc. from the top of the dryer.
Be REAL CAREFUL not to knock any of the wires off of the timer switch.
Then remove the top of the dryer.
Remove the lint filter, and the two screws that hold the lint filter housing in place to the top of the dryer.
Remove the front of the dryer. This will expose the drum and belt.
Remove the drum and belt and this will expose the drum rollers, idler arm
pulley and motor.
Now is a good time to check the belt to see if it has slipped off of the
idler arm pulley and also to check the belt condition for wear.
Be sure to note the route of the belt, this will come in handy when you go
to reinstall the belt.
Check your drum rollers for flat spots or wear, if they have flat spots
or wear on them replace them.
If the drum rollers don't have flat spots or wear on them then they probably
only need lubrication. Lubricate the shaft of the rollers with a good grade
of machine oil such as 3 in One oil.
Reassemble the dryer, plug back in. This should solve your noise problem.
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