the Thai embassy in Denmark specifically says 50+ AND on a pension for a non-o based on retirement. However there has been wrong information from them previously.
no notification regarding acknowledge the payment - it is done immediately if the receiver has registered Promptpay and if he has not registered Promptpay then he can't receive a promptpay payment and the sender can not send money to him that way - he could then use QR instead
when you open a bank account you can choose to register promptpay with your phone number. That number is then linked to your account. That's why Promptpay works. You can't use the same number if you want to setup promptpay in another bank. I have Bangkok Bank with promptpay. When I opened an account in Krungsri I could not register Promptpay with the same number. When I checked the registration of my number I saw it was already registered in Bangkok Bank. A clever system. You could have used QR payment if the receiver had not registered PromptPay