I had non/ OA visa which expired last Oct 18 after one year was told just go across the border come back and you will get another year the border guard ask if I would be leaving the country again I said no. But I forgot I was going on a cruise and just got home. She stamped for one more year, so I thought I was good till Oct 2020. So we fly back from Singapore and they only give us 30days. Now they tell me I should have filled out a re- entry permit. So make sure you ask before leaving.