Eastern Chan

Hi there, I had moved to UK from Hong Kong 3 years ago. I maintained the employment with my employer in Hong Kong and work remotely in UK. As my employer does not have any business in UK, I did tax return by Self Assessment and income tax had been paid. However, I was not informed for contribution of any class of National Insurance. Could you advise whether I should have National Insurance contribution? If I need, what kind of National Insurance contribution should I do and what is the procedure to apply? Thank you very much for your advice.