As seen from your communication, it seems that income earned from abroad is showing an increasing trend. Hence, it is worth while to start paying the necessary taxes and file the tax return.
The due dates for filing the tax returns for year ended March 2017, 2018 have lapsed. You still can file March 2019 return as the date for belated return is extended to June 2020. Also, note the due date for filing the MArch 2020 return is now extended to Nov 2020. I would advise you to pay taxes from MArch 2019 onwards. The chances of receiving notice are less as the numbers are small.
There are various penalty for non-filing return, interest for not paying advance tax, declaring wrong information or misleading information. Also, there is fixed fee ranges from 5000-10,000 for non-filing return within specified dates. Notice can be issued till 4 years from the end of assessment year. There are possibilities that notice can be issued till 6 to 16 years, but not apply to you as the amount involved in meagre.