The melody of the National Anthem may not have changed between the old monarchist government and the communist one that has prevailed since 1975, but the words have, of course, been "reviewed and changed" after the events…
See the difference between before and after the revolution…
The actual National Anthem (since 1975)
For all time the Lao people have glorified their Fatherland,
United in heart, spirit and vigor as one.
Resolutely moving forwards,
Respecting and increasing the dignity of the Lao people
And proclaiming the right to be their own masters.
The Lao people of all origins are equal
And will no longer allow imperialists and traitors to harm them.
The entire people will safeguard the independence
And the freedom of the Lao nation.
They are resolved to struggle for victory
In order to lead the nation to prosperity.
(Extracted from the website of Maps Of World)
The National Anthem during the time of the monarchy
The Lao race was once of great renown in Asia,
Lao’s were united and loved each other,
Today they still love their race and their country and group themselves around their King,
They have preserved the religion of their fathers and they know how to hold on to their ancestor’s soil,
They will not allow a foreign nation to come and trouble them or to take their land,
Whosoever would like to invade their country will find them resolved to fight to the death,
All together they will restore the glory of Lao blood and help each other in times of trial.
Extracted from the site Forum Lao. You can even listen to these hymns in MP3 format.