The overall matter for 嗨 is never "tone", stupid or not.
嗨 is vocal, usage translation is "hi", and created from "Hi", the usage is glimmick and illusive, simply improper and nowhere applicable, but maybe unofficially cute for its existence.
"hi" is an english greeting, in Chinese, we'll proper say "你好", "早上好", "新年好", etc..
It has been some years that there is a trend to play with chinese words to produce illusive titles, but to make excitements.