Laotian Army would probably win. Thailand has a very corrupt and
sorry military and will remain such until people are desperate.
US would intervene as Reagan is assumed to be president in TL POD.
Most bomb tonage overwhelming was flown from Thailand during
the Vietnam war, not as force fed to the media gullet from GVSN or
Guam. The president of Thailand (PM?) asked us to leave in 1976 to
accomodate the newly communist neighbors.
But expect some territory to be lost, as akin 1963 India/PRC conflict.
Worthless acres and not tankable. But US assisted incursions across
the Mekong would be a ready threat as something about half of Lao
population live 30 miles from the river/Thai border, including the main
capital.
Try this link as the other does not work. Also be advised that
some googled results have virus indicated, in my recent experience.
http://en.wikipedia.org/wiki/Thai–Laotian_Border_War