Sam Smith & BF Brandon Flynn Safe to Say This Relationship's Lit

1/25/2018 6:35 AM PST

Sam Smith Shows BF Brandon Flynn PDA After Japan Return

Sam Smith and his boyfriend, Brandon Flynn, put on a smoke show ... literally.

The Grammy singer and "13 Reasons Why" star snuck in a quick cigarette break -- and a kiss -- Wednesday night outside of Gemma restaurant in Soho ... where the couple dined with a few friends.

PDA was definitely calling -- Sam had just returned from Japan. Their silly sides were also on full display ... walking an imaginary runway with different strides.

It might have gone down something like this.