@Eri ***********
Chaeng Wattana can do it in about 30 minutes once you get to the front of the queue when you go there. Have your new bank letters, updated bank book that morning, and copies of your passport pages, and your ready to go for the type O retirement extension. The purpose of the first 90 days is so it gives you time to get your bank account set up and the bt800,000 in it for the minimum two months. Being you already have that, ask the immigration officer when you can come back to get your full one year extension, as you might be able to do it the next day. From my understanding that 30, or 45 day timeframe only applies to extending the yearly extension, not your first 90 day. Be sure to ask. With a ligitimate agent you'd have to go there anyway. They help get your documents in order, and then only save your spot in the queue so you don't have to stand there longer than needed.