Who is green bank? I can't find any reference. KBank/Kasikorn?

Be aware that MasterCard adds a percent or two to the interbank rate, then Santander add another half a percent on that. Halifax use the raw MasterCard rate. But that's still not as good as the Visa rate. Wise generally give the Visa rate (on card) or better direct although as you say it can fluctuate a little. Wise bank to bank was better than the best Kasikorn rate when I checked (only checked once).

That's only when using the card, not direct transfer to Thai account

You get the TT rate, either when you transfer into a THB account, or when you convert from a Bkk bank USD account into Baht. Isn't as good as Wise, Currency Fair or dedicated brokers.

Also has a branch in London, you get the TT rate plus 500 fee, which isn't quite as good as Wise, a dedicated broker or currency fair

Appointments at the US embassy in Ethiopia are booked up 2 years in advance. Thailand better but presume that's why Brandon says this is important.

Short version: check currencyfair and dedicated brokers such as global reach, but Wise comes extremely close (within 0.13% when I checked) and is easiest and most transparent, and can support limit orders (where an exchange is triggered by a certain rate).

Longer version when I looked into it a few weeks ago:

Global Reach just gave me a quote, £20k 6th Dec 5pm gmt+7, 42.59 no fees, so 851,800 (haven't clarified but assume 500 Baht receiving fee would also apply)

Interbank at time 42.7467.

Bangkok bank TT buy at time 42., net 845,950 Baht

Wise at time 42.7570, £110 fee (0.5%), net 850,430 Baht

Currency club 849,867

Currency fair 851,923 (assume receiving charge of 500 Baht to come off too)

So Global Reach better than Wise but only by 900 Baht / 0.1%

Currency Fair better than Wise by 1,100 Baht / 0.13%

On CurrencyFair and Wise, you can put a limit order, or automated transaction, that triggers if a rate reaches a given level. These need time and care, but are great for grabbing a rate that is only available briefly due to a momentary spike.

On cards, the Visa rate is best, adds just 0.3% to the ECB interbank rate, which is what Wise gives. MasterCard add 1-2% more. So spending on card too, Wise comes out a percent or two better than even fee free Mastercards.

Yes I've pointed out that their website says unlimited, but they just repeat that you only get one assist for free. They claim to assist with driving license, but charge 3000 if you want them to get the residence certificate as well as using up your free assist presenting it to driving authority. I find it dishonest, and petty given how much Elites cost - we paid 1,100,000 Baht, and they want to charge another 2-3,000 to bring an additional document. That said they do give good instructions and these things are mostly pretty easy, eg, banks recognize the Elite card. Airport service is really nice, golf cart from plane to the visa fast lane, escorted through, while baggage is collected, to a plush car waiting.

Elite do also charge for most of those, you only get one assist for free, then it's 2000 baht plus each time.

Thank you very much Steven, very kind of you to delve into such detail. Some interesting food for thought. I reckon I can probably rule out marrying a Thai, but I'll double check with the wife as you never know..

For anyone else curious, I think the middle bit of Steven's post was about whether it is better to pay an agent $2000 to borrow their 800K which they'd draw down to 400K (didn't realize you could do this), or use your own if you have it or borrow.

I believe you need to extend before 60 days, to get the final 30.