I have a Student Visa. It is an "m" visa. Meaning multiple entry.

I went and extended it for another year at the Sathorn office.

My question is: do I need a re-entry permit?

Basically i have a sticker visa for 1 year, and I extended to Jan. 2010.

Do I need a re-entry stamp???????

Yes, if you are planning on leaving the country and want to retain your extension of stay.

If you left withot getting a re-entry permit and used your visa you would get a 90 day permit to stay which would cancel your permit to stay that you got from the extension of stay you got at immigration.

So yes you have to get a re-entry permit at immigration.