Thin clients are simply diskless workstations that use terminal services to connect to a server. They often do not have hard drives or operating systems and installation of software on the workstation is not possible.
System Five uses the remote POS device manager for handling all the POS devices locally for cloud and terminal services (RDP) clients. Thin clients may not be able to run the POS device manager. Implementing Thin clients is going to be costly and lengthy in terms of support, installation and additional cables etc.
Windward Software does not recommend thin clients for POS stations that are connecting to barcode scanners, pinpads, slip printers, cash drawers as most of these devices use USB drivers that do not connect over terminal services. While most thin clients have USB ports, they usually only support mice, keyboards and printers.

Pinpad Support on thin clients

Pinpads are not supported on thin clients connecting to System Five Cloud
Pinpad and Server must be on the same local network.
Pinpad needs to support TCP/IP (Ethernet) connection and will need its own network cable. Please check with Windward Software for pinpads that support TCP/IP for your version.
RS-232 Serial cables may also be supported, but not USB to Serial, ie your thin client must have a build in RS-232 serial port.
See this link to change the pinpad setting to TCP/IP