DeeMoney, as mentioned above, may work but it does have a Bt800k daily limit. I have used them a number of times for transfers to UK, but far less that your requirement (around Bt400k in total). Once registered no demand for any paperwork to show source of funds /visa or WP status, but that may depend on value of transfer / multiple transfers. My transfers, if set-up around 8am, were in my UK bank same working day by around 4pm Thai time.
They are running an iPhone 13 promotion just now for cumulative transfers of Bt5m until 31Jan22 so that seems to imply they may have no issues with multiple high value transfers.
https://blog.deemoney.com/iphone13airpodpro/?fbclid=IwAR2E2LNtTNO1nfTOilyFJi9GJewlA9m7-P020Ruu0aZHBgUtLH2kxIbRxFE