Chris Brown -- Glowing Probation Report -- Judge Orders LESS Drug Testing!

Chris Brown's been partying his ass off, but as far as the judge in his Rihanna beating case is concerned ... he's been a model citizen -- and his reward will be fewer random drug tests.

Chris was in court in L.A. Wednesday for a progress report on his probation, and the results were glowing -- all his random drug tests were negative and he attended bi-weekly therapy sessions.

So the judge agreed to cut the singer a break, and scale back the number of drug tests from 3 a week ... to just 2.

Pretty impressive for a guy who had to be carried out of a club back in June.