Jeff Bezos, Lauren Sanchez Sail French Riviera, Massive Diamond on Display

Jeff Bezos has his fiancée Lauren Sanchez doing all the heavy lifting during their latest globe-trotting trip -- and, no, we're not talking about their luggage.

Lauren's 20-plus carat diamond boulder was on full display -- loud, proud and blinding -- as the couple pulled into the small village of Beaulieu Friday in the South of France.

She was wearing a low-cut orange maxi dress while Jeff kept it casual in a tight tee and white pants ... aka vacay Bezos-mode.

The ring's so damn big it really does look like she's doing bicep curls when she raises her hand!

TMZ broke the story ... Sanchezos initially tried to keep their engagement under wraps after he popped the question in Spain.

She turned the ring around so the diamond wasn't showing ... but once they had some friends aboard the $500 million superyacht, there was no keeping it secret.

BTW, they're back aboard the Koru for this trip right now. As we've seen in recent days, Jeff is doing some work ... as her personal photog -- he snapped shots of Lauren rocking a bikini on the yacht's deck.