I want to open Apple ID account to make payment to purchase Apple products from Bangladesh. How can I do it?

How to create a new Apple ID - Apple Support

But if you are posting on this forum, yoiu already have an Apple ID.

As for purchasing items in Bangladesh:

Availability of Apple Media Services - https://support.apple.com/HT204411 - "Learn if you can buy apps, movies, music, books, and more, or use Apple Podcasts or Apple News, in your country or region."

iCloud storage plans and pricing --> https://support.apple.com/HT201238

- If your country is not listed then you cannot buy anything (and there is no need for a payment method).