What does the Japanese word Mondai ga rai mean in English?

"Mondai ga aru" (問題がある) means "there is a problem" or "there's a problem". "Rai" (来) means "to come". Therefore, "Mondai ga rai" (問題が来) isn't a standard or grammatically correct phrase in Japanese. While you could *construct* a sentence using those words, it would need more context to make sense. It might imply something like "a problem is coming" or "a problem will arise," but it sounds unnatural.