Final note, as you may have read Wise has restricted the banks it will/can send to. Although Krungsri is listed on their list of possible banks there is another thread running on here where people are getting transfers rejected to banks on that list. I would highly recommend you make a trial transfer as soon as possible to ensure that you can actually use Wise if you choose to do so for the extension money.
Actually just checked the app which now says other banks are 500,000.
Recipient bank
Maximum per transfer (THB)
Bangkok Bank Public Company
2,000,000
Kasikorn Bank
2,000,000
Siam Commercial Bank
1,499,999
Other recipient banks
500,000
When I did my first extension last year all my transfers to my account were done using Wise from the UK. I always selected "funds for long term stay" as the reason for the transfer but at least for my bank, Kasikorn, it makes no difference to how they show on the statement, all transfers, irrespective of reason, show up as international (I'm not entirely sure that's even important).
Nope, he didn't need to check your code because he can see on his system that you've done it. If you hadn't you'd have been sent away to get it done. Random codes will not work.
No you cannot connect a Thai bank account. Where are you telling it you live/have residence? You will need to prove your residency in that country to set it up.
They don't want the hassle, there's no money to be made from it. Better let the destination deal with it. As has been reported many time lately with Brits carting massive bags of the stuff to the UK.