We caught Ray at LAX Thursday and he proudly told us all about his fresh ink, while also delivering a message to the people sounding off, largely in disapproval, of the piece.

The "Sexy Can I" singer told us ... he got the tattoo of Brandy to show his love and appreciation for her. Ray J says, without her he wouldn't be who he is today.

And, he clearly wasn't phased by the standard social media shots, some of which -- hilariously -- came from Brandy!

Ray says she was a bit uneasy about the style of the tat -- which depicts Brandy with blood-red eyes and the words "Best friends 4 ever" on her face -- but he likes it and that's all that matters to him.

In fact, he doubles down saying anybody who doesn't approve is trippin'. In simpler terms ... "It's my leg, and my sister".

When Ray posted the image of his tattoo, he called it the "holy leg" and said it was "real gothic-like." For anyone asking, he says that's just the artist's style.

Of course, this comes a few months after Jack Harlow admitted he didn't know Ray J and Brandy were siblings, which stunned lots of folks on social media ... given that Brandy helped Ray J start his career.