Cat i think possible by cargo, but i am not sure 100%, there is a grup for flight volunteer on facebook, I used them twice for my dog to Europe, Try to find them in Flight Volunteer Pet Thailand, i guess, i dont remember. Hope this can help.
We did. But normally its your HR will do for you, you dont pass the airport before you cancel by your company. They might ask you when you will come back.
Just tell to your company that you resign and HR will tell immigration to cancel your visa.