Forrie J. Smith claims he got booted off a plane for being drunk ... but he says it's really because the passenger sitting next to him was wearing a mask.

The "Yellowstone" star shared a video to Instagram where he says he's just been removed from a plane after telling someone -- unclear exactly who, but presumably flight attendants or others in positions of authority on the craft -- he didn't want to sit next to someone wearing a mask.

Smith -- who has to be reminded what airport he's at -- says they kicked him off the aircraft claiming he was drunk, but he asserts he's only had a few drinks and absolutely isn't drunk.

Forrie then calls out an unknown, unnamed group of people for not standing up and calling out all the "bulls***" surrounding wearing a mask ... and reiterates the mask on the other passenger's face made him uncomfortable.

Forrie -- best known for playing Lloyd Pierce on 45 episodes of the hit show "Yellowstone" -- captioned the video, "You need to hear this story" ... and, it's raising a bunch of eyebrows online.

There are a lot of people in the comments asking Smith why he cared if someone else on the plane was wearing a mask ... with many adding personal anecdotes about why they'd wear a mask while traveling.

BTW ... this is all par for the course when it comes to Forrie's beliefs. He previously said he wouldn't attend the 2022 SAG Awards because he's unvaccinated.

In that vid, Smith says he's totally anti-vaxx -- even going as far as saying he doesn't vaccinate his dogs and horse ... no doubt an extreme position.