You don't need to file anything when it comes to income from pensions. The Revenue Department is not going after retirees living on income from pension and imo they never will. Don't listen to scaremongers. Just relax.😎
The problem is where he's officially staying. Having an account in Pattaya Chonburi while staying in another province is not very smart. There might be problems when applying for the 1 year extension.
The fee at KBank when receiving money from abroad via swift is maxed out at 500 baht. The minimum is 200-250 baht, I honestly don't remember the exact amount. There's no receiving fee for transfers via Wise.
Why just KBank and only in Pattaya? You can also try KBank on Jomtien Beach Rd. Just take the baht bus from Pattaya straight to the bank. If you're on a 90 days Non-O based on retirement but staying in another province than Pattaya, you'll have some logistic problems doing 1 year extensions.