Permission of parents to be a Monk I already know this much    https://buddhism.stackexchange.com/a/35802/17220
Still ,there is a particular case where ,I have no experience/knowledge which is below.

Person with 27 yrs. of age and above. Parents are alive. No responsibility over Person. Person is having exemplary character &amp; is unmarried. Person is unsatisfied by any meditation center , monastery , ashram , yogi etc. ,so want to meditate alone in forest alongside other *religious meditators. Parents are not ready to accept buddha or buddha's teachings for their child cause they think that it(buddhism) is only to destroy householdness. It tears down parents if person flees away to forest or even tries to do so. 

Update 

Under these circumstances, is permission required ,if yes ,then how to convince parents. 

Note:: 'To be a monk' means 'to go forth to be' :: 

detached one , beyond all sense of his own name and form. Without any existence of I, my or mine. Not to grieve if his name and form entity were to decay and deteriorate.
This rule is put in place because joining a monastic order (like any thing else one does in life) is a karmic act, and one should strive not to do harm. The idea that a child might disappear into a monastic order, never accomplishing any of the 'normal' things that parents expect of children — gainful employment, grandchildren, social status or respect, or any of the other hallmarks of worldly 'success' — can be frightening and disturbing to a parent. One is asked to seek parent's permission so that one does not enter monastic life leaving a cloud of fear and resentment in one's wake. It's an act of compassion for parents and the world they live in.