Another route for you
For people paid a salary or wage, the employer deducts professional tax from the pay and pays it to the government (section 5); you need not register yourself. No tax on a monthly salary up to ₹15,000; ₹150 a month for ₹15,001–₹20,000; ₹200 a month above ₹20,000.
Instead, see:
If you have more than one employer, or another class in the schedule gives you a higher tax, you can give your employer Form III or Form IV and enrol and pay yourself; then choose the "business or profession on my own" answer in this guide.
You cannot get this
Under entry 39 of the First Schedule to the professional tax Act, agriculturists, people performing religious duties, the listed skilled workers (goldsmith, blacksmith, pot maker, basket maker, washerman, barber, cobbler, tailor, carpenter, mason, plumber, book binder, toddy tapper, electrician), people with a disability of 40% or more, and dry cleaners are exempt from professional tax. You need not register.
You cannot get this
If the tax for your class in the schedule is Nil, you do not pay professional tax. Under the Act, only those liable to pay the tax must take an enrolment certificate. Check again when turnover crosses ₹10 lakh or when you complete 5 years in the profession. With a GST registration, a PTIN may still be issued automatically.
Not confirmed: The department's pages do not say in so many words that a person at a Nil rate need not enrol; the Act ties enrolment to being liable to pay. If unsure, ask your Profession Tax Officer (PTO).