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You didn’t elaborate in what conditions you are getting salary in HK. There could be a scenario where your present company send you here for few years onsite project or other work related activities. So, you are getting your basic salary in HK but you also get your onsite salary. You can reach out IRAS to find out if you need to declare two earnings or not. But, what I know is that you won’t pay tax which is as earned in HK.

By regulation, you get taxed on income paid for your job in Singapore, no matter where and how it is paid. You may not get taxed on payment for services performed outside the country and which are not incidental to your job in Singapore.
You better contact IRAS with your exact situation. It's their job to figure out what applies in your case.

I am a student pass holder in singapore...how may I get SPass in singapore .I want to work here.

You need to read forum’s earlier discussion. You can’t hold two passes at same time. Under student pass, you can’t work full time. If your student pass allows to work part time and your institution has no objection to it then you can work part time during weekends but that has to be checked with your institution administration.

Any work pass, only can be obtained when you are hired by an employer for a full time job and the employer apply work pass for you and MoM approves your work pass. Good luck