@Surya maroju This scenario came up two weeks ago in our meeting with the web apps product group. Their response was that running multiple sites in a single web app was not officially supported. As @sadomovalex pointed out, there might be unofficial methods to achieve this but as with anything unofficial, you run the risk of it breaking in future updates as it's not a scenario that will be validated during testing.
You can run multiple web apps in a single app service plan at no additional costs., which was the recommended approach by the product group.