It is possible as i did it to my mother up to nine months. all you have to do is go to the main immigration office and let captain sign your extension. just tell the captain that you need your mother to stay for one more month. most of the time he signs the extension. but if he don't sign it come back the next day. The captain is very nice person just need to ask him nicely as well. oh one more thing. you need to be there before 7 as he always leave around 8 in the morning.