[3] In 1959, she moved to North Vietnam where she studied primary and secondary school, and in 1975, she graduated with a bachelor's degree in finance from Hanoi.

She was successfully re-elected in the congressional representative election in February 2002 and was promoted to the vice chairman of Congress in April of the same year.

[8][9] In December 2010, Laotian Prime Minister Bouasone Bouphavanh resigned and was replaced by the then President of the National Assembly of Laos Thongsing Thammavong, and as a result, Yanthou succeeded Thammavong as the President of the National Assembly of Laos.

She was also re-elected to the Party Central Committee and the Politburo at the Ninth Congress of the Lao People's Revolutionary Party held in March 2011 and on 17 May 2014, she and other senior government officials did not get on the An-74 of Lao People's Army because they suddenly changed their plans before the departure and took another plane hence avoiding the ill-fated aircraft which crashed while en route to Xiangkhouang Province, killing 16 of 17 occupants onboard.

At the Tenth Congress of the Lao People's Revolutionary Party in 2016, she was re-elected as the President of the National Assembly.