Found preview is looks ok but if i open it, it's showing another drawing, please advise.

What is the exact version no. (e.g. v10.x.y.z) of MicroStation that you are using? Use key-in VERSION to see the version no. in the MicroStation Message Center, or Help→About MicroStation in the backstage.

See this blog that shows you how to obtain MicroStation's version number.

Thumbnail

From MicroStation Help: The system creates/updates the thumbnail image using the view that was active at the last time you selected File=>Save Settings.

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Jacob isaeq said:

if i open the file it has showing the Y (different) drawin

If you File=>Save Settings (Ctrl-F), do you see the correct thumbnail image?

Still no, for Ctrl + F no "save setting" has been window opened? 

did you  open the file and then do a save settings