How can I extend my entry visa for medical reasons while in Thailand?

I wonder if you can advise I will have been here in Thailand for 2 months on the 9th November on an entry visagiven at the airport. On the 8th November I need to be admitted into hospital to go through a complex spinal surgery not knowing how long the post-op and recuperation period might take, before I can actually leave to go on to Hong Kong. How do I manage to get an extension in this particular case? I'm already in a wheelchair and hard for me to move around. Thank you in advance. Ani Zamba