You will need to create an Azure support ticket, specifying that you would like your subscription to be able to disable Hyper-Threading.
After that, you can disable Hyper-Threading (HT) by adding below tag when you provision the Azure VM. If the VM already exists, you will need to restart the VM to make it effective.
Please add the tag “platformsettings.host_environment.disablehyperthreading” and set it as “true”.
To check if you are running a hyper-threaded VM, run the lscpu command in the Linux VM.
If Thread(s) per core = 1, then hyper-threading has been disabled.
If Thread(s) per core = 2, then hyper-threading has been enabled.
Raymond's Tech Notes 