Hi Ashish,
Please try as follows
CALL FUNCTION 'GUI_UPLOAD'
EXPORTING
filename = lv_filename
filetype = 'ASC'
has_field_separator = 'X'
TABLES
data_tab = lt_upload.
.
IF sy-subrc <> 0.
* Implement suitable error handling here
ENDIF.
It was working fine in my case for Chinese/Japaneese text.
Does the data comes correct in internal table ?
Also, opendata set can be used instead of gui_upload, so that it will read the contect from document directly.
Regards,
Nivedita