I don't know your language and neither the meaning of the letters of your font, but you should look into the hyphenation section in your paragraph styles.
The reason for this was already explained to you in a previous thread, along with a method you can use to prevent it in this file if you don't want to spend the time required to replace the font.
InDesign recognizes Unicode character mapping. The font you are using is not Unicode compliant, but instead is a re-mapped ascii font. The character at which your words are breaking is mapped to the _ character, so ID thinks it can break there. To do a proper fix you need to replace the font, with a Unicode compliant Hindi font, and there are several, and use a series of Find/Change operations to replace the text character-by-character with the correct mappings or start fresh with a Unicode compliant font and the proper keyboard method.
You can use this file as it is if you add a GREP style to your paragraph styles that applies No Break to characters you don't want to break.
The fonts we are using are not unicode compliant, can we change the mapping of our font as per the unicode ?
I dont' want to change my font, because its being used at lot of places (i mean lot of books)
If we can do character mapping using script that will be helpful ?
The only way to change the character mapping is to edit the font. That essentially makes a new font.
The mapping script is useful only for the case where you are changing from your current non-compliant font to an different font that is Unicode compliant. The ONLY way you are going to be able to use the current font in ID and prevent this break is using the No Break attribute wherever that glyph is used.
Buy a new font, an OTF version. I am sure that you can get your font in a modern file type. That would be the most cost effective way to handle it.