Hi Chang Hong,
If the screen turns off mainly after the laptop is locked, Windows uses a separate Console Lock Display Off Timeout, which can be different from your normal screen saver or display timeout settings. Microsoft documents that the locked-screen display can turn off after 60 seconds by default. (Monitor powers off after 1 minute when PC is locked)
You can check this by locking the PC with Windows key + L and observing whether the screen turns off shortly afterward. If that matches what you're experiencing, the console-lock timeout is likely the setting to investigate rather than changing the screen saver again.
If it only happens while locked, that distinction should help identify the relevant setting without repeating the troubleshooting you've already tried.