Birthday Bieber bling! Justin Bieber knows how to do his lady right on her birthday and he did just that for wifey Hailey on her birthday - slash - Thanksgiving.

Hailey showed off the sparkly tennis necklace adorned with her new last name and some pix of her enjoying her birthday cake and sharing a "sweet" kiss with Justin as she had whipped cream smeared on her face.

But it wasn't all fun and games, folks, JB got serious as he celebrated the holiday ... he posted this introspective message the day after Thanksgiving ...