If you live in Nakhon Si Thammarat you will note that Thai Immigration in Nakhon Si Thammarat will be able to assist you with all your visa extension and 90 day reporting issues. If you have a work permit and need to do your 90 day reporting then you can do it at their offices.
Note that you can also apply for a re-entry permit if you are leaving Thailand and wanting to return again without invalidating your current visa status. Speak to them as listed below for more information and assistance.
Thai Immigration in Nakhon Si Thammarat
1/1-2 Amphoe Mueang
Tel: 0-7532-0727, 0-7534-6679