My sponsor told us that living with Myanmar National is illegal in Yangon with out any marriage. And that its ok to live in with foreign boy friend or partner under the same roof but NOT ok and its illegal to live with Burmese partner.
Also, by living with Burmese Partner will destroy their institution image.
I am not sure if all these are true but If you have similar experience, please do share with us. We are talking to a lawyer to figure this out but we would like to hear it from you. Thanks a lot!