I arrived in thailand, 12/01/10 with a mutli entry visa which was stamped till 11/04/10. I am staying in Nakhon Sawan. Now where do I go just before the 11th of April? I thought it was Nakhon Sawan immigration office but they told me I have to go to Mae Sot( even though on the wall in big letters it says 90 day extension). Did I speak to the wrong man or do I have to go to Mae Sot? If I do what papers do I need to take? What is the post like and is that an option? If I need this form TM47 can I get that at Nakhon Sawan Immigration Office?

If anyone can help I would be most grateful

You have to leave the country and enter another. Then return.

Any border will do.

Your confusing with 90-day reporting which is done when you are on 1-year extension of stay.

You a multiple entry visa that means that you must make a border crossing every 90-days.

Correct. The normal procedure with a valid multiple-entry non-immigrant visa is to leave the country just before your permission to stay date expires and re-enter Thailand thus receiving another 90 day entry stamp.

Thanks for that I have to go to Mae Sot cross into Myanmar and come back, do I just need to take my passport or do I need any other papers?

Passport, your arrival card and money will do.

Under certain circumstances you can get a 1 year extension from immigration, if you tell us on which grounds you have a multiple non-immigrant we can tell you about the criteria for your case.