This poem is in first person, from the cloud's perspective.
At the beginning of the poem, the cloud is describing the good things it does, like bringing "fresh showers for thirsting flowers" but toward the end of the first stanza the cloud sort of becomes violent, describing rain and hail. In the second stanza the mood shifts back to more pleasant things, as the cloud sleeps.
The cloud and thunder are two different entities. When the cloud says "he" this means the thunder. The cloud is not referring to himself. He is distancing himself from the thunder.