How to I disable the DHCP function on Wi-Fi Tethering I want to have a Static configuration for wi-fi tethering because there is no way to change the IP range.
I think you cannot disable the DHCP in the Hotspot. Instead try to set static IP address on clients(other devices which you are going to connect).


Connect the client to wifi hotspot.
Now check the ipaddress of the Client. It should be like 192.168.42.yy 
Go to 'WiFi settings' on your client, long tap on the Hotspot's wifi
Tap on “Modify Network”.
Then select “Show Advanced Settings”.
Select IP settings from DHCP to ”Static” mode.
Fill the following



  IP address : 192.168.42.&lt;your desired ip&gt;
         Gateway : 192.168.42.yy
         Net Mask : 255.255.255.0
         Prefix length : 24
         DNS 1: 8.8.8.8
         DNS 2: 8.8.4.4


Note: If your give IP address in 192.168.1.xx or 192.168.0.xx range, It will not accept.

If you are a nerd, See this to change  the coding of Android system itself to achieve static IP :)