This is his advice on your question of what to do with 7 days overstay three weeks ago:
@Tod ********
. Okay, the way it works when you clear an overstay of under 90 days (where you're not banned) IS
you can go to the immigration office, pay the overstay and leave the country THAT day
OR
you can go to the immigration office, pay the overstay and buy an 'extension denied' 7 day stamp for 1900baht to get out of thailand in a week
OR
you can just pay the overstay at the border when you stamp out of the country.
Using any of those options are not gonna cause you any difficulties at a thai consulate getting a new visa.
Face it you're not the first foreigner in the history of thailand to overstay.