Udonis Haslem was so frustrated with his teammate Jimmy Butler during Wednesday night's game ... he threatened to beat the star's "ass" in a team huddle.
The chaotic scene went down during Miami's home game against the Warriors at FTX Arena ... when Jimmy Buckets and UD almost came to blows during a timeout.
Haslem and Butler, who had been sitting down, were arguing ... when Udonis appeared to yell, "I'm not your f***ing kid," which prompted Jimmy to stand up from his seat.
Haslem then began shouting, "I'll beat your ass!