If it only took you 10 minutes you must be very tech literate. It takes much longer,having to upload the pictures satisfactorily. Not easy at all, but if you're used to these it will be easier.
A lot of people are not tech savvy, or don't have smart phone.
I'm. thinking the safest way is to book for 4 weeks in order to get Thai pass easier then try and get extension when there and if successful change the return flight date