Andrew i was back in England 5 or so yr back and got it renewd at london . But google the website renewing passport Im now on retirement exstensions with monthly income proof I find it easier than border bounceing
Its Chong Chom you cross into Cambodia as Kap Chong is the immigration office 5 or so kilometers before
I done this border bounce for all my 90 days for 7 or 8 yrs
The only problem i had in all that time my pasjnsport filled too quick
Its not nessasary but i used to give one of the Cambodian Touts 1 or 200 baht and he filled the forms out not that their hard and he went and brought me my 200 cigerette allowence when i smoked