I make customization on payroll and i want to hide my custom folder (source code) from the customer server, how can i hide the source code??
This depend on how you configured your client instance. If you are having single odoo instance and if you are looking to hide some modules from a particular database, it wont be possible it will show all the modules from the addons path.
Here what you can do is that, create multiple odoo instance in same server and you can use one instance for your customers with specifying necessary addons path in conf file and other one for you. Once you have multiple instance you can specify the addons path separately.
For Settings Multiple Odoo Instance, see: How To Run Multiple Odoo Instances in Different Ports of Same Machine