The Rae Sremmurd rapper took to X Sunday to vent his frustrations with VP Harris ... straight-up telling people to do more research on the Biden administration first before casting their ballot.

Lee also replied to a debate clip from when she ran for president before the 2020 election ... capturing Tulsi Gabbard tearing into her record as a prosecutor that's resurfaced since Joe Biden dropped out and endorsed her last week.

Lee ranted about tax money going toward foreign aid ... claiming he's sick of seeing his money disappear toward war efforts that don't directly involve the USA.

It's a long rant from Swae Lee ... and one that's getting him a ton of negative attention on social media -- with many shocked because SL's never been big on sharing his political opinions.

In fact, many are questioning how much research the rapper has done himself ... or if he's just concerned with his own bottom line. Just look up Swae Lee on X if you want to see more brutal condemnations.

Swae has opened up about his pro-Republican leanings in the past ... including pointing out how Donald Trump pardoned Kodak Black and Lil Wayne late in his presidency -- adding DJT's totally tapped into the culture.