In order to separate two opposite charges, work must be done.
Remember that whenever work gets done, energy changes form.
As the monkey does work on the positive charge, he increases the energy of that charge.
The closer he brings it, the more electrical potential energy it has.
When he releases the charge, work gets done on the charge which changes its energy from electrical potential energy to kinetic energy.
Every time he brings the charge back, he does work on the charge.
If he brought the charge closer to the other object, it would have more electrical potential energy.
If he brought 2 or 3 charges instead of one, then he would have had to do more work so he would have created more electrical potential energy.