Cosmic and Modern
If you come across another Dylan Thomas poem, chances are you'll see some cosmic stuff similar to "And death shall have no dominion." He's not exactly known for being a "down to earth" kind of guy. He liked to think big and write big, tackling death, the cosmos, and just about everything in between.
Long story short, our man loved imagining the different ways the universe works. He tried hard in his poetry to bridge all those gaps in life that tend to separate us here on earth. In other words, you might hear ideas about day, night, ghosts, and the sea all within a few lines. In a lot of ways Thomas tried to keep it all together while maintaining that sense of universal unity of all things.
At the same time though, we know he was also part of the modern poetry camp, although he wasn't one for labels either. That means you'll hear a lot of experimentation with rhyme, meter, and the overall language of the poem. The guy wasn't looking to make things easy on us.