According to a new report from Radar Online, Tristan hasn't learned his lesson about sleeping around behind Khloe's back.[/url]

Tristan allegedly hooked up with Lani Blair while he was in D.C. with the Cleveland Cavs.

We know that Thompson has been in contact with Blair recently, but we assumed he was smart enough to at least keep the relationship platonic.

Turns out, we were wrong.

“Tristan’s so sneaky,” says one insider.

“He wants Khloe to have a break from motherhood and go back to LA for a week or two to be with her family. He’s telling her she deserves some girl time with her sisters, cocktails in the sun and the warm LA weather.”

First of all -- warm LA weather?! C'mon, source!

Last we checked, it's June everywhere, and Lake Erie isn't north of the Wall!

Anyway, what really matters here is not the insider's knowledge of meteorology, but their claims about Tristan's ulterior motives:

“The truth is, Tristan wants some time away from Khloe so he can be with Lani,” the informant says.

“He told Khloe he’ll take care of all her expenses and take care of baby True in Cleveland and wants to put Khloe on the next private jet to L.A.”

Yes, apparently Tristan still has “serious feelings" for Blair, and he just doesn't know how to quit his stripper side-piece.

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“He misses those fun times and Lani makes him feels so good. He wants that type of comfort right now, especially since he just lost the finals,” the insider claims.

“He’s not ready or in the mood to deal with Khloe, hear her run her mouth or work on their relationship just yet.”

Oh, man.

Hopefully, he doesn't use the phrase "run her mouth" within earshot of Khloe.

We're pretty if you talk about a woman in those terms just weeks after you cheated on her while she was pregnant with your baby, she's legally allowed to murder you.

Tristan's on the thinnest ice known to man, and dude just tried on a pair of concrete boots.