はい and ハイ

[mrdeanop2]

Does both はい and ハイ mean the same thing?

[Psy]

Yes. You can think of ハイ as an italicized version of はい.

[percent20]

Any reason for that specifically?

I thought katakana was used for foriegn words that were brought to japan? are there any more specific rules on it?

[jkid]

Not really rules, Katakana is sometimes used for Japanese words for emphasis as Psy said as well as just to seem "trendy".

[gerald_ford]

That, or for sound effects in Manga and such.