Permission of parents to be a Monk

It is possible to find a monestary that will let that slide. Some are more flexable and take the rules as guidelines instead of law to be followed rigidly, not out of laziness but out of wise practicality and out of an attempt at a sense of what the Buddha might do in today's times.

Also relentlessness in your dedication to break into the monkhood is often a help as they like to know you are serious.

Person is unsatisfied by any meditation center , monastery , ashram , yogi etc. ,so want to meditate alone in forest alongside other *religious meditators.

Then he isn't immediately seeking an ordination as that would usually entail integrating into an existing group for which such an allowance is to be obtained.

I hope the person figures out a good solution ensuring a comfortable & safe abiding; not subjecting themselves to unnecessary hardship and stress.

It is going to be difficult to be a yogi without ordination because going forth in the dispensation of Buddha Gotama without a formal ordination is very uncommon. As it is, it is often asked of one to complete a trial period before being given a formal going forth which is like a meal ticket to an extent.

Imo a yogi without formal association is more likely to be assumed to be an outcast holding wrong views, unable to get along with 'the contemporary masters'. Therefore it will be difficult lest one makes a living recycling stuff or otherwise gets the money.

It tears down parents if person flees away to forest or even tries to do so.
It seems person is having very strong bond/attachment with h-is/er caring parents.

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.
That's an obvious reaction from parents who have not been established in dhamma or they are established but worry about person's capability. Even buddha used to question, when his disciple/s want to go to dangerous/full-of-dukkha places to preach like with the case of 'poorna'.
Moral:: You will have to prove in front of them that you are worthy of independent homelessness.

Under these circumstances, is permission required ,if yes ,then how to convince parents.
Surely, there is a way for someone aspiring to be established on Noble 8 fold path, a 'middle path'.

If parents are very caring, person might start by bearing his own responsibility first, slowly-slowly increasing independent-meditation-time, slowly-slowly showing parents about his/her calibur of asceticness and decision making capability.
Wait for the right time, start reducing any communication-gap among relation.
No caring parent wants to harm his/her child or to be a cause for any harm. It's just the worriness about safety that they pretend to act as a barrier. Understanding them from their perspective will enable person to see/feel them as Helpers in person's decision.

If parents are not so caring, then tears might be out of society-fear but such perception requires one to be very hard-hearted.
In this case, person must make his stand in society first. Person should start by bearing his own responsibility first••• same-as-before ••• decision making capability, ultimately leading him/her to win over everyone's ego.
Wait for the right time, start reducing any communication-gap among relation and society.

With right time and right understanding, person will surely be able to take his/her decision of independent-meditation(asceticness).

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.