What is the year and model of your Jeep?
When does it make the thumping noise - braking only, all the time, on acceleration, etc?
Where just the brake pads replaced, or was the more done on the brakes?
If thumping is occurring on braking, is there any vibration or pulsation felt in either the steering wheel or the brake pedal?
Any roaring noise, or just the thumping?
You need to have the front tires checked for belt separation - this is the most common reason for the noise you are describing under the conditions you have described.
Will the thumping stop as soon as brakes are applied at higher speeds, or does it slow down and stop at a much lower speed?
Usually if its the brakes, there will be a vibration associated with it, but you can take of the driver's wheel to make sure that rotor is flush against the hub, and the caliper bolts are both in and tight. Also make sure the caliper is not cocked at an angle.
If ok, I would suggest rotating the left front to the left rear and see if the thumpin either subsides or comes from the rear as I suspect it is a belt separation
The thumping can subside when the load changes when making a right hand turn, especially if belt separation is on the inner side of the tire- load comes off of it so the noise goes away. turning left keeps the load on it, so the thumping remains.