Tyga laughed off Blac Chyna's accusations he's skipping out on child support payments, as he sped off in a Ferrari ... while shopping in Bev Hills. 

Yeah, this clip is dripping with irony ... Tyga was leaving Barney's NY when we asked about BC's rant, where she called him a bitch for not paying and talking behind her back.

He says a lot here, even if his mouth isn't moving that much.

As for the yellow 'Rari -- we'll see if it works out better than his red one.