This is not going to be easy. You may need to go to Bangkok; take Stumpy's advice above, but in the meantime gather photos showing the 2 of you together and reasons why she would want to return to Lao, eg her own bank account with a decent amount of money in it, deeds to any land or property she owns etc.
Tough one to pull off. She needs to be employed in Laos with decent income. A nice balance in the bank. Clean Police record. All in All, its a headache