Whenever I try to close the Thinlinc client it immediately reopens. This occurs whether I close through clicking the x button, right clicking the taskbar icon, or killing through Task Manager. I am running Windows 11 OS and am using Thinlinc v4.13.0.
The ThinLinc client has a --loop option, which will re-launch the client each time it closes (meant for “kiosk” or thin client situations). It may be that the icon you are using to launch the client specifies this option.