That's normal, it just need to keep trying. Where are you, as someone maybe about the suggest a branch. There's also the option of getting a agent to open account for you. 5000 baht I think I have seen posted on here
They asked me , although I have all the correct documentation, they still were going to refuse boarding before I managed to convince the manager they didn't know what was required.
My understanding of the requirements is a ticket out , means of transportation irrelevant. 🙏
You also don't have the 400 baht continuously in the account. Like many things in Thailand they only exist on thin ice and the authorities will always have a way if they want to infalse.
I opened a Bangkok bank account in Chiang rai. I will come back to with the branch . I also had a residency certificate from Chiang rai immigration 500 baht .