Marc Malkin

Lindsay Lohan is setting off another round of wedding-bell rumors.

LiLo was spotted wearing a ring of diamonds on her left ring finger while lunching with Samantha Ronson yesterday at Tuscan eatery E. Baldi in Beverly Hills.

But they're not picking out new china patterns just yet...

"Sam and Lindsay are unbelievably happy and in a healthy relationship," a pal of the couple tells me. "And like any couple in love, they speak about marriage and the future, but right now, there is no wedding planned."

Lohan's rep did not comment on the ring.

The pal says Lohan probably wore the sparkler to—shocker!—create "some more buzz."

A few hours after lunch, the two held court at a dinner party at West Hollywood's Matsuhisa restaurant to celebrate Ronson's 31st birthday.

No doubt Lohan will be by SamRo's side when she deejays next Thursday at the opening party for nightlife impresario Allison Melnick's new Apple Lounge on über-trendy Robertson Boulevard in West Hollywood.