The name is apparently Dutch [*], and thus an English pronunciation will only be approximate. It ends up as "Hork" (rhymes with "pork"). They play with this in the show and intentionally mispronounce it "HO-ack" or "HO-ehk" from time to time. His first name rhymes with "pen," of course.
[*] From what we know about Ren's cousin Svën, he is Danish. It seems like both Ren and Svën are a mixture of different European cultures.
From Serge K. (firstname.lastname@example.org):
In entry 4, there's an entry about the pronounciation of Ren's name. As stated there, it is a Dutch name. Well, I live in The Netherlands and watch R&S on the BBC.
So here's the addition. In the Dutch language, "Hoek" is spelled just as "Hook" in the English language. You just have to give it a somewhat sharper sound to the "oo"-sound. But, there's an umlaut on the "o", and in the Dutch language, it's impossible to put it there.
So there's only one conclusion: Ren is German! It's the only language that supports his name with the umlaut. The pronunciation is still the same... So just keep it as "Hook"...
Editor's Note: There has been a conclusion reached on Ren's name. His
name, according to Comics Interview #131, came from