"A man who does not drink"
Translation:마시지 않는 남자
Can someone explain why 감자 comes last instead of first in this sentence? Is it because of the topic particle on the verb?
Yes, the verb gets a topic particle because it's acting like an adjective to describe the noun, thus it goes before the noun.
It's actually not a topic particle, it just happens that conjugating a verb to make a relative clause often looks like one. This is the phrase "the doesn't-drink man". It's actually more convenient than English, because in Korean, descriptive phrases come on the same side of the noun as descriptive words (adjectives, like "tall") do.