People who are in the country on a Visa exemption, VOA 15/30 or a Tourist Visa (TR60) etc can be eligible for a "short term" extension.

You can apply for this extension at both immigration offices: 
Phuket Town Main Immigration Office ( Room 101 on the ground floor )
Patong Beach Immigration Office

Medical extensions can only be done at the Immigration Main Office in Phuket Town.
Please select one of the sub pages for more information.