I am living in Phuket...I have a Multi Entry Type O Visa and it is time to make a Visa run. Can I do the run to Myanmar? Or must I fly out of Thailand and fly back in?

It might sounds like a stupid question but I have been told a few different things.

Thanks

You can enter through any Immigration Checkpoint you want and get 90 days.

It does not matter. You will get a further 90 days permission to stay on re-entry as long as your visa is valid.

On my entry stamp its says its good until September 28, 2009. Does that mean I have to make my Visa run on September 27th or September 28th?

On the 28th. The only time when you have to be early is the visa expiration date for entry.