Long Term Visa Requirements for My Daughter

Hi Everyone,

As some of you might know, I shall me moving to Hanoi with my 2 year old daughter in October. We shall be living with my fiance (Vietnamese National) and soon to be wife.

Now a little background. I work away from home (at the moment Iraq) and because of the nature of my work, I return to my loved ones on a rotational basis. On my present rotation, I am away for 9 weeks and return for 3 weeks at a time. I understand that it is possible for me to apply for a multi-entry visa for both of us, but I am concerned about how to arrange a long term visa for my daughter. I am led to believe that after we marry, this will be a lot easier, and not so much of an issue, but we will not be marrying until January 2018.
It would be a strain for my fiance (but not impossible) for her to take my daughter out of the country every month or so on a multi-entry visa, but I am really looking for a more permanent and stable solution for my little girl.
I am hoping that someone on here may be able to advise, or at least point us in the right direction.
Many Thanks

Bill