Your thread should be titled "How safe is the agent supplied retirement ....". Many of us just do it ourselves so there are no surprises as immigration law is very clear.
Q1. Typically how long does this refund take to come into your account?
Q2. The KBank mobile app to register for PromptPay does not allow for non Thai National IDs. Is PromptPay for foreigners even possible with KBank?
My KBank works. You need to have an active Thai phone SIM in your device working also. It does not need to be on international roaming but using the SIM over WiFi will suffice.