Mera is a name, so the phrase simply indicates that the speaker is thinking about someone named Mera.
It's important to note that this phrase is incomplete without context.
For example:
* "Estoy pensando en Mera." (I am thinking of Mera.)
* "Te estoy escribiendo pensando en Mera." (I'm writing to you while thinking of Mera.)
The meaning of the phrase will vary depending on the surrounding context.