Sam Ronson -- Check Out My New $800k Lady Nest

Lindsay Lohan's ex-girlfriend / neighbor Sam Ronson has officially moved on to bigger and better things ... 'cause the DJ dropped over $800k on a sick new house in Santa Monica.

Sam recently ditched her Venice pad -- which famously sat right next door to LiLo's place -- and picked up an 1,170-square-foot bungalow earlier this month ... just a few miles away in a different beach town.

The 2-bedroom, 2-bath crib is pretty sweet too ... rockin' hardwood floors, a completely finished backyard, fire pit ... and best of all it's 7 blocks from the ocean.

According to docs, Sam managed to drop $184,500 for the down payment -- leaving her with a $625,000 mortgage.