How early can a British passport holder apply for a 30-day extension at Jomtien immigration office?

A British passport holder needs to apply for a 30-day extension at the Jomtien immigration office. It's mentioned that applications can typically be made within the last week before their current visa expires, but some users suggest trying to apply a bit earlier if the applicant has specific difficulties. It's advisable to contact the immigration office directly to explain the situation.