To be classed as a traditional Lao girl, it doesn't mean that she must always wear the traditional Lao sinh (long skirt) or that she has to stay home 24 hours a day, but she must be a good person.
To define a "good" traditional Lao girl, she must obey her parents, follow buddhist practices, help out with chores at home, work or study, not drink heavily, dress appropriately for the occasion, has never worked in any naughty places, and socialising should be done during the day and she is expected to be at home once the sun goes down.
A traditional Lao girl usually lives with her parents until she gets married and she is a virgin. Although having said that, the younger generation of Lao girls have found ways to have sex and still be good girls.
So, anyway, some of the respectable places to find a traditional Lao girl includes a Lao party, ceremony, festival, shopping mall, school if you're allowed into the premises, and through a reliable friend or relative.
If you are serious about finding a nice Lao girl and building a meaningful relationship, then a traditional Lao girl is the answer to your prayers. In general, they are stable, trustworthy and most importantly, they possess the qualities needed to be a good wife.