According to the footnotes given in Cindy Mao and Ma Baolin's Sing Chinese "Wa Ha Ha" is a Uygur folk song. This is one of the most popular folk songs from Xinjiang, where the uygur people are known to be a cheerful and upbeat people. This song clearly shows their spirit and character.
Very happy stuff too, dear surfer.

Verse 1.
This land of ours is pretty.	wǒ men de zǔ guó shì huā yuán.
It is full of fresh flowers.	huā yuán lǐ huā duǒ
Basking in the warm sunshine	hé nuān de yáng guāng zhào yào zhe wǒ men
Everyone puts on a smiling face	měi gè rén liǎn shàng dōu xiào kāi yán
wa ha ha wa ha ha	wa ha ha wa ha ha
Everyone puts on a smiling face	měi gè rén liǎn shàng dōu xiào kāi yán
Verse 2.
Big sister will you hurry up	dà jié jie nǐ ya gǎn kuài lái
Little brother will you join us too	xiǎo dì di nǐ ye mò zǒu kāi
Hand in hand we sing a song	shǒu lā zhe shǒu ya, chàng qǐ na gē er
Our life is full of joy	wǒ men de shēng huó duō yú kuài
wa ha ha wa ha ha	wa ha ha wa ha ha
Our life is full of joy	wǒ men de shēng huó duō yú kuài