Ray J isn't backing down from challenging Mario in a singing battle ... despite his opp not taking the competition too seriously.

We caught up with Ray in NYC mid-morning Tuesday, where he was advocating for a TMZ After Dark and Brunch Tours in the Big Apple -- a move which definitely has a nice ring to it. Play video content

After all, Ray has become quite the Hollywood draw with our bus patrons, so an expansion may be on the horizon!!! Play video content

Back to the matter at hand ... Mario and Ray are currently in a volley of words about singing superiority, and Ray demands some respect be put on his name.

Ray recently attempted to crash Wale 's homecoming stage in Baltimore alongside Mario, only to be stiffed ... so now he has smoke with the "Lotus Flower Bomb" ra

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