Just returned from a very enjoyable liveaboard to the Similans. But the thought does occur that you are a long way from the hospital if you have an accident or another major medical emergency while you are out there. Realize it may vary depending on the operator, but what happens if you do need medical care on an emergency basis?
Depends on the kind of emergency and the operator and their Emergency Assistance Plans.
SOP: head back towards the main land with the boat, depending on the kind of emergency call a speedboat to meet the boat or go to the main land with the boat.
From their transportation to the chamber in Patong for diving emergencies (all the time breathing oxygen).