Hi Ben
right in the centre of the old city, near Wat Chedi Luang
land size is about 84 sq wah (330sq m., house size is around 130sqm plan, not incl courtyard)
as for planning, it taks about 6 weeks in the old city and they are fairly strict
however, TIT so it depends on who you use to submit your plans
they have to be careful as the neighbours tend to complain about any obvious infractions; there is a block of flats nearby that cannot be completed due to complaints and not being in accordance with the laws