Tyga -- Seals Music Video Deal with Drake's Ex ... With Handfuls of Her Ass

Tyga just upped the ante in his pissing match with Drake ... by grabbing a giant handful of his ex-chick's ass and signing her to co-star in a new music video.

Sources involved in the deal tell TMZ ... Tyga asked Dollicia Bryan to be in his "Make It Work" video specifically because the song includes lyrical jabs at Drake, like -- "Ni**a never was my homey ... all these bitches know you corny ni**a."

Drake's been flirting with Tyga's baby mama Blac Chyna on social media for weeks now -- so, not shocking that Tyga bagged Dollica.

In fact, we're told Tyga flat out told Dollicia he was using her to piss off Drake ... and she jumped at the opportunity.

Exes be trippin'.