็How to use "こちらこそ" ?
i heard this word many time but i still don't understand it.

Question

็How to use "こちらこそ" ?
i heard  this word many time but i still don't understand it.

Answer

I think it is one of the expressions that is not used in other language very often. 
The feeling that we have with this word is "from me, too", "it is I who should say so", "the one who should say so is me", etc.

For example: 
A: Nice to meet you. (よろしくおねがいします。)
B: Nice to meet you, too. (こちらこそよろしくおねがいします。)

A: Thank you so much. (どうもありがとうございます。)
B: Thank you, too. (こちらこそ、ありがとうございます。)
     (It is I who should say "thank you".)

I hope this was helpful.

Answer

Hi,nice to meet you.
it means "chen kan"(in Thai).

we use just like this;

Thank you(ありがとうございます）
not at all (chen kan)(こちらこそ）

Answer

Use after よろしく always helps.