The final manufacturer reply about this problem was like that:
The reason which could happened in the power supply one or both of the following reasons:
1. Laser tube metal pole not isolated as should be
2. The machine and power supply not connected 100% to the earthing
I have good earthing connector in my workshop and I am sure from it. So, the only reason will be the laser tube isolation!!
Please, if any one give me an idea to be sure from the isolation of the HT line which is connected to the laser tube it will be very helpful
Thanks in advance