Emily Ratajkowski Sunbathing in Tiny, Barely-There Bikini -

Emily Ratajkowski's Down Undah in Sydney

If ya got the Monday blues, Emily Ratajkowski in white -- a super tiny white bikini -- is exactly what the doctor ordered.

Emily's soaking up some sun in Sydney right now, lounging around with a gal pal who, TBH, is holding her own next to Em. Still, when it was time to snap their personal pics ... you can figure out who posed and who played photog.

The barely-there bikini Emily's rocking leaves VERY little to the imagination, and based on the pics -- click through the gallery -- she wanted to pay homage to the classic 2005 Jessica Alba pose.