I'm going home to the US and taking my Filipino wife with me. She has her US visa and we're leaving June 24. She presently has a Non-B visa and I've heard word that she will next to cancel the visa first and get a letter from the school for her last day of employment or she will not be allow to leave?

My question is if she leaves through Swampy will immigration want that letter or not? Some of her friends have left and no mention of wanting a letter. Is it only the border crossings looking for the end of employment letter?

Does she actually have a Valid visa obtained outside Thailand from a Thai Embassy or Consulate?

Or does she have something stamped in the passport which was obtained in Thailand from an immigration office ?

She has a Non B stamped on her passport from Thai immigration office and will expire next year in April and she also got her US immigrant visa this month. We are planning to go to US next month. Does she need to cancel her Thai visa first before leaving for the US or just leave Thailand without cancelling her Thai visa via the airport?

Seems she may have a "extension of stay" not a "visa "

However, you seem to the expert and therefore I would suggest you do what you believe to be "right" .

She has an extension of stay not a visa. A letter to cancel the extension is not needed at the airport.