One QBO account is for one company file.
Should you need to manage multi company files, consider having a single one time license of QB Desktop US version. Deploy a private cloud if required.
Hello there, martinvarghese-c.
In QuickBooks Online, each company requires a subscription. You can sign up using the same username and password for all companies. You can use this link to sign up: https://quickbooks.intuit.com/in/.
If you have an existing QBO account, you can consolidate all other companies under one username and password. Here's a link for the detailed steps: Sign in to multiple QuickBooks Online companies with one user ID.
Let us know if you need anything else.