The speaker of "Drinker" is someone who drinks to escape their own head. The first line sets up a strange split: "I fortify myself against myself." Fortifying is what you do to a castle before an attack, so the enemy here is the speaker's own self, and the drink is the wall they build. The word also hints at fortified wine, which makes the line double nicely as a pun.
The second line gives the reason: "what I fear is thought." It's a blunt, honest admission. The trouble isn't the world outside but the endless running of the mind, especially when things go quiet. Then "I order disorder" works as a neat paradox. Ordering a drink is an act of choosing chaos, a deliberate step into blur and confusion because it feels safer than clear thinking.
The final line, "o night," reads like a sigh or a plea. It's brief and a little romantic, but also tired. The mood is lonely, wry and quietly desperate, all held in very few words.