@All, There is one field "Payment Amount" (Field id : payment) in customer payment record in Apply sub tab. I am getting error "An nlobjSearchColumn contains an invalid column, or is not in proper syntax: payment." while using nlapiLookupField or nlapiSearchRecord for getting value of this column in the client script. Any help will be appreciated.

I'd suggest that you create a Saved Search from the UI first and then export the code using the plugin: https://chrome.google.com/webstore/detail/netsuite-search-export/gglbgdfbkaelbjpjkiepdmfaihdokglp