What is じゃねんじゃ.. My friend say it is Tsukkomi but I don't get it

Question

I posted this タイからこんにちは！ in the web somewhere with my Twitter ID. And then there is someone new followed me in Twitter with a tweet タイからこんにちは！ じゃねんじゃ in his timeline. I wonder what that actually means..

This is used by tsukkomi player? How?

Answer 1

It's a dialectal (jocular) expression with a little slack spelling.

じゃねんじゃ
→ じゃねえんじゃ (restoring contracted vowel)
→ じゃないんじゃ (non-vulgar form)
→ じゃないんだ（よ） (Standard Japanese equivalent)

So, it means something like "No way it's that ~", or more tsukkomi-like:

"Hello from Thailand"? Oh, come on!