You should use Phone.ShellAsync to run a script with these commands. I'm not sure whether it will give your app, which runs in a different process, the required permission.
Thank you Erel for the answer. I have tried Phone.Shell earlier but unfortunately not working. If I enable serialport from Terminal Emulator with script above, my code - and any other that use this port - working well. It seems can't change permission from my code. I know should use USB to serial converter easier but I want to use the built-in serialport of ODROID instead. Is another solution or need to give up?