What documentation do I need to bring for an extension at the IT Square immigration office in Bangkok?

Update: thank you to everyone who lended assistance. I’m now sitting in the food court below immigration, feeling a sense of accomplishment. 🤣🤣🤣. I’m now (sort of) over my fear of immigration. The woman at the counter was fierce 🙂 and this is coming from someone described as fierce herself, but I have my stamp.

I am amused that my stamp is until 5/12. I will be leaving Thailand and returning before that date. I expect a bit of a head tilt at immigration since they are so accustomed to folks trying to live here on visa extensions and border runs, lol, but so be it. Again, thank you!!!

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Original post: Ok, I’m really sorry for this question. I swear that I’ve searched the history of the group, but I’m not finding this precise answer. I know it must be there, but I’m not seeing it.

I forget all the terms, but I’ll try to answer all relevant questions and avoid the snark as best as possible:

I’m American (that’s what immigration forms call me…there’s no such thing as United Statesian)

I will be in Bangkok

I was stamped in with no visa…whatever term that is

I am unexpectedly, but happily, needing an extension. My main question is, what documentation do I need to bring? Do I need to get a copy of the TM30 from the hotel or do I just need to bring my passport? What else might I need to bring?

Also, I’m staying at Phrom Phong. Is the closest immigration office that Short-term visa office at:

C039, C040/3 อาคาร IT Square, Chaeng Watthana Rd, Talat Bang Khen, Lak Si, Bangkok 10210

I only have a couple days in which to handle this due to my travel plans, so I want to make sure that when I go in, I’m fully prepared.

Thanks so much.