Hi,
Is there any way to disable Pi-hole service for specific client without change the DNS address on his computer?
Im using Pi-hole DHCP service but its not possible to manually set DNS address for static IP address.
Yes, it is possible, follow this guide.
Edit: Take a look at this thread
If you have a MikroTik router, or any other router with the same capabilities, you could use a whitelisting rule for your IP addresses. I created some automated commands for my MikroTik which allows users to bypass filtering on the fly by visiting a specific URL.
I posted here Temporary bypass by IP address