Q.cutting leaves on ponytail palm bonsai
Can I cut off all the leaves on a ponytail palm bonsai tree? I had purchased a ponytail palm bonsai tree. All the leaves on it turned brown. I don’t know why. But I cut them all down. Now all the leaves are falling down like they are about to fall off. My question is could I totally cut the tip of the palm off? Will it regrow??

You cannot prune off the top of a Ponytail Palm. It would likely die from fungus.
If you plant has lost all of it's leaves, it has likely died and will not grow back it's leaves.
Overwatering is most likely the issue, Ponytail Palms are sensitive to overwatering.
Here are some links that will refresh you on the care requirements.
Check the care and wait and see.
https://www.gardeningknowhow.com/houseplants/bonsai/bonsai.htm
https://www.gardeningknowhow.com/houseplants/ponytail-palm/pruning-ponytail-palms.htm