Apparently, some wall chargers can damage the Ricoh Theta. Here are the symptoms and some suggested solutions.
Some users found that when they plug in their Theta to a wall charger, there will be a red light as if it’s charging, but after they remove the Theta from the charger, the Theta doesn’t turn on anymore, as though the Theta battery can’t hold the charge. It appears that this problem is caused by some wall chargers. Once this happens, it appears the Theta will need to be sent back to Ricoh for repair (which is usually less than the cost of a new Theta).
The safest way to avoid the problem is to charge the Theta by connecting it via USB to your PC. Other users have recommended only wall chargers up to 1.5 amps or less, although I don’t know what is the maximum amperage allowed for the Theta.
Here is the link to the related discussion on Theta developers forum.