Question

causes of frequently changing of constitution in nepal

Answer 1

Now the monarchy is abolished in Nepal. Just like India in the Nepal democracy have started recently.
Now they have President and Prime Minister of Nepal by the election of the people of Nepal.

Answer 2

In 1948, The Government of Nepal according to the Act enacted for democracy was replaced because there were no constitutional powers given by the Constitution of Nepal.

The primary representative constitution established in the year 1959 was dismissed by the King of Nepal because he considered that the constitution is attempting to overcome his abilities.

In 1962,  again the constitution giving democratic rights was dismissed after a short-term period of time because it was deemed as the anti-democratic in nature.

In the year 1990,  the Constitution was amended third time by the Ruler of Nepal because he wanted to modify the constitution of the country according to his selfish wishes.