@Nicko *****
okay lets try NOT to make it any harder than you have to ๐
You need a MINIMUM of 15 days left on your current stamp to apply for the in country Non-O visa at Chaengwattana for 2000baht.
You DO NOT need a booked appt (it just makes it faster), If you don't have an appt you get a queue number and just queue up with everyone else.
SO if you're not going to the immigration office with at least 15 days left on your stamp, you go to Laksi and get the 30 day extension FIRST,
then you can go to Chaengwattana and apply for the in country Non-O visa in Section C-1