I am currently holding an expatriate pass in Malaysia. I would like to fly to Hong Kong for a few days, then continue my vacation to LA from Hong Kong. Will there be any issues since I am not flying from my residing country? I am a Singaporean.
I don't see why there should be an issue.
You are a Singaporean national and being a Malaysian Resident should not be an issue at all. Singaporean nationals are allowed to travel visa free to Hong Kong for up to 90 days, which I believe is lesser than your intended period of stay.
From there, you are free to board a flight to Los Angeles (United States) wherein you are allowed for up to 90 days at a single go as a part of the Visa Waiver Program (VWP).
Make sure that you fill out the ESTA(Electronic System for Travel Authorization) beforehand and there will be no issues.