Not sure if US entertainment industry is a fair comparison, many US BLM singers got negative records but still popular.

Anyway, Namewee is not conventional artist relying on  conventional media to publish his songs/mv. His mv on YT alone can put many artists in shame. Not to mention he write his own songs, produce his own mv, pretty much no need to rely heavily on others unlike most pop song singers.

Lets assume that the lab did the due diligent and the result is true, all negative.

unker dont belip the lab result can be bought (rasuah) in such a high profile case.

Then, the question will be how accurate is the test kit? and why the police so generously giving out case details so freely?

the test kit accuracy is 85–95% per test. Total 3 tests, cos 3 different drugs.
if really all negative, police need to sue the suppliers.

update: from GPT

Yes, pseudoephedrine can cause a false-positive result on an amphetamine urine drug test (UDT) due to the similar chemical structures of the compounds. A specific study reported a false-positive rate of 75% with one common immunoassay test (Microgenics DRI amphetamine-methamphetamine immunoassay).