Who else besides PhD holders are qualified to use Singlish in Singapore?

In a letter to the New York Times, Prime Minister Lee Hsien Loong's press secretary, Ms Chang Li Lin, rebutted Singaporean poet Gwee Li Sui's opinion piece headlined “Politics and the Singlish language“. In rebutting the poet Ms Chang said, “not everyone has a Ph.D. in English Literature like Mr. Gwee, who can code-switch effortlessly between Singlish and standard English, and extol the virtues of Singlish in an op-ed written in polished standard English.” But besides PhD holders, who else are qualified to use Singlish?