David Spade -- Amanda Bynes Is Still HOT ... She's Got Great Boobs

Despite all the craziness ... and the wigs ... and the legal drama, David Spade says he still sees Amanda Bynes for who she really is -- a hot piece of ass.

Spade was hangin' at The Improv last night with his "Grown Ups 2" co-star Nick Swardson -- when Dave dropped some serious truth bombs about the ongoing Bynes saga.

"I'm scared of Amanda Bynes," Spade said ... joking that she'll call him "ugly" on Twitter if he says anything unflattering about her.

But Spade did rank Amanda's hotness -- and it's obvious, he's a fan.

"If you cut out all the 'stuff,' ... she's technically, for all intents and purposes, very pretty -- but I think she's getting in her own way."