If you're going to be transferring money in regularly, only 3 banks allow international transfers of 50,000 or more per time. Bangkok, SCB and Kasikorn.
I had one transaction to Bangkok bank not coded as international. I went to Kasikorn (Wise's partner in Thailand, and the bank the transaction came through on the way to Bangkok bank) and got a letter verifying that it was an international transaction.
But immigration never noticed it wasn't coded as international. In the 3 years I've been transferring money in every month, that's only happened once.
And as stated, use the 'funds for long term stay' reason in the drop-down.