I was applying for an O-A visa extension with multiple entries. Before anything else, I went to the TVC office in Bangna to get a feel of the company. The "Grace" I met was very clear in her explanations, and very friendly. She took the pictures that were needed and arranged my taxi back. I plagued them with quite a few complementary questions afterwards by email to alleviate further my anxiety level, and always got a prompt and accurate answer. A messenger came to my condo to get my passport and bank book. Four days later, another messenger was bringing back these documents with a new 90 day report and brand new stamps. Friends told me I could have done it myself with immigration. I don't dispute it (although it would have cost me 800 baht of taxi and a day at the immigration office plus probably not the right documents and having to go back again). But if you don't want any hassle for a very reasonable cost and zero stress level, I warmly commend TVC.