How can we access application context inside companion object in Android kotlin?
You can not. Your options are:
A) Provide the context as an argument to all functions that need it.
B) Instead of a Singleton companion object, create an instance of the class and provide the context as a constructor argument. Consider closing / cleaning up the instance, when not used anymore.
C) When your Application is initialized, store the application context in a globally accessible variable / property. This is arguably the most dirty solution.