helper('url') vs Thai language agrument = Error

[eluser]Unknown[/eluser]
Hellow everbody .
I have my problem again about url and Thai language agrument.

Code:

in my controler .
redirect("admin_excute/submit_add_place_type/argument"); // work in english language.

//but i want to send agrument in Thai language .
//it is error .
// display : The URI you submitted has disallowed characters.
// my url : http://localhost/travel_thai/admin_excut..._jpeg.html

�_าษาไทย3<-- this is thai language

How to i send agrument with Thai language
befor : i change my file to utf-8 in controler and views but dose't work.