Open files with thinapped application

Hi.

I have create file associations for few thinapped applications (Adobe Reader, Microsoft Word).

First file is opened as expected. But next time I click on file it start new process of

thinapped application, after few seconds it closes and file opens in existing windows.

It is significantly slows down opening files in thin application.

Is it normal operation? Is there any way to open files in existing window (process) at once?