No, you don\’t need to register again. Once a student registers with ICAI, his/her registration is valid for next 5 years.
You just need to fill the exam form for May 2019 and pay the required fee and you are good to go.Most probably the exam forms will be opened in February 2019 so keep an eye on the important dates.
For the time being, just start preparing for May 2019. Good luck Himanshu.