Fans were quick to slam Tristan for leaving such an inappropriate comment.
One insisted: "Stop it" while another told the star: "Please don't ever take him back."
A third said bluntly: "Guess you didn't appreciate what you had until you lost it. The grass isn't always greener. Tough life lesson."
Another wrote: "Stop embarrassing yourself Tristan you'll never get her back she's to good for you."
Khloe and Tristan had a highly publicised split after he was famously caught out kissing Kar-Jenner family friend Jordyn Woods at a house party.
This isn’t the first time Tristan – who shares one-year-old daughter, True, with Khloe -has made a desperate attempt to flatter his ex.
Earlier this month he told her he was "so proud" of her winning a People's Choice Award.
Posting a picture of her on the red carpet, he wrote: "Congrats Momma Koko on winning best reality star 2019, that's two years in a row.
"Two time champ. I love the sound of that. So proud of all you have accomplished this year."
He even sent her a congratulatory balloon when she launched a new fragrance earlier this year.
Meanwhile, Khloe doesn’t even follow Tristan on social media.