Chances are that nothing bad will happen to you during your time on Koh Phangan but it is very wise to be prepared for an emergency in any Country you travel to.
It may not be yourself in an emergency situation, you may come across something that needs urgent attention or in any case there are a few numbers you should add to your phone right now.
Although it can be unnerving in a foreign Country try to remain calm as help is in place to assist you.
Use your own phone or locate one with the closest person if you come across or are involved in an accident or emergency situation.
Emergency Phone Number - 191
(They will then put you through to the right local location emergency contact)
Other emergency contacts;
Ambulance and Rescue - 1554
Medical Emergency Call - 1669
Tourist Police - 1155
We have an article on what to do if you have an accident which you can read here but ALWAYS call for help in any kind of accident or emergency.