That might depend on how "oh" sounds to you. Do you mean "oh" as in "oh no!" pronounced by an English person from the south-east? (well, RP is what I mean)?
I'm not sure even if Welsh has that sort of "oh" sound. Their "o" seems to be a different "pure" vowel sound, as in "go iawn", and when a Welsh person speaks English with a strong Welsh accent, say using the word "gold", it doesn't sound quite the same as an English RP speaker saying it.
(and it doesn't sound like Welsh "w" (to me) either).
Oh, the limitations of text for representing sound! I've tried learning IPA, but I don't find it easy, and I'm not even sure that's 100% reliable anyway).