Tom Sandoval and Rachel Leviss are still in touch -- at least in one direction -- 'cause one of them is wishing the other a happy birthday ... even though they seem to be miles apart.

Rachel posted a video Sunday showing off where she's been hanging out lately, and it looks lovely -- a beautiful farm setting with a garden of flowers all around, which she's enjoying to the max. Her caption was, "I've been dreaming of a place like this."

While the clip went up 2 days ago, TS just commented on it Tuesday ... which is Rachel's 29th birthday. He wrote, "Happy Birthday Rachel, I really hope ur finding peace and happiness. Miss u friend."

Rachel hasn't responded ... but a lot of other people have, and most of the reactions to his unprompted shout-out aren't great. As you might imagine, folks are telling Tom to buzz off.

Seems the wounds of the cheating scandal are still fresh for many fans ... even though most of the '"Vanderpump Rules" cast is already moving on -- as cameras have been rolling for a new season, sans Rachel.

Remember ... she stepped away to deal with her mental health in the aftermath of the combative reunion, and at this point -- there's no indication she plans on coming back to L.A., at least for the time being anyway.

Meanwhile, Ariana Madix has a new man ... and Tom appears to be linked to a new flame.

And yet, he still has Rachel on the brain -- despite all they've been through.