is it possible multiple Return Authorization from Sales Order??

You can for different items (cannot return the same item more than once, so if you generate a second RA it will only include things from the SO that weren’t already on another RA). We actually wrote a tool to allow you to return the same “item” more than once - a button that creates a RA that includes all lines on the SO. We needed this because in our line of business, you can partially return something (insurance - partial return premium if something changes).