How can 2 objects have the same temperature but different amount of thermal energy?

First thermal energy (heat) is not the same thing as temperature. Thermal energy is internal energy held by the molecules but the temperature is the is the effect of the heat. Temperature is the measurement of the heat energy. Also, thermal energy depends on the size of the matter but the temperature isn't, it's just the average heat energy held by the matter.

Magma  is composed of molten rock and is  stored  in the earth's crust. lava is  magma  that reaches the surface of our planet through a volcano vent.