For the past few years I have done my extensions based on marriage at the immigration office in Central Festival Mall - much easier, less crowded and better parking. I began using an agent to prepare everything many Years ago after doing everything myself for over a decade and am very happy to not have to deal with anything any longer. All I do is sign my name many, many times. My agent does everything for me for a very nominal fee - under 10,000 baht including the immigration fee of 1,900 baht and also including all of the 90-day reports for the year.