Showing ฿500k wasn't the issue. I provided a statement + balance confirmation from my HYSA showing significantly more than required.
I applied under the workcation category. In order to prove that I work remotely, according to the consulate's own website, I needed to provide an employment contract OR an employment certificate OR a portfolio of clients. I provided a stamped+signed certificate from one of my customers AND a contract with that customer AND invoices to the customer.
Apparently this stack of documents still wasn't tall enough, so it was rejected and my ฿10k was refunded (best thing about applying in person - they refund your fee!). I was told the officer wants to see a bank statement showing those invoices being paid into my checking account. It wasn't an unreasonable request, I guess, but it just wasn't a requirement anywhere I looked earlier. Oh well.
Other than that unwarranted (imo) initial rejection, I have to say the experience at the consulate is... lovely. No huge lines (6-7 people at most whenever I was there, and I arrived at my leisure way after they open the gates), no standing in the sun/rain endlessly, consulate employees are helpful and calm. Very relaxed and enjoyable in comparison to pre-appointment years.