I m arriving Hong Kong Airport today in even 5 pm and I have my flight at 7 from HK to Singapore.

No, the airport shuttle bus doesn't operate for 24 hours. They depart at about 10-minute intervals from 05:54 to 23:28 and approximately 12-minute intervals from 23:28 to 00:48 daily. Thus, according to your situation, you are just advised to find a hotel nearby the airport. And then you can easily catch the next flight in that early morning. Notably, passengers need to arrive at the airport at least 2 hours in advance.