This is our uniquely colloquial language, Singlish. It’s nothing wrong since it’s part of our identity. The problem, I’m afraid, is that students thought that that is the standard language. It’s truly a battle for us when they come in with such a notion. There’s once when my students asked me if I came from Britain!!!?? I was merely speaking standard English (I don’t believe I spoke with any accent)!
Being able to distinguish between Singlish and standard English is important and thereby, code-switching.