As a German u get 30 days on a flight in not 2 weeks.and can extend it for 30 days more here at the immigration for 1900 thb. But they check now how many times you have been in and out this year.....so maybe be better get the 60 day tourist next time and extend this......
U need the form from your owner as well and if he not does it you have to have the power of attorney as well most private owners don't do it, they are scared of paying taxes