Just bumping this thread to note that having just moved to a new iPhone, whilst the above still works for the TTB app, I hit a stumbling block with the Krungsri app. Having submitted my bank account and passport numbers on the identification page this popped up, "Digital authentication is required before using Krungsri app. Please bring your ID card to update your photo for digital authentication registration at any Krungsri branch near you."
I thought I'd done the digital authentication back in May, I was getting constant reminders to go and have my photo taken, so when I obtained my new bank card, I also asked them to do this. The notifications ceased. Anyway, my wife rang Krungsri this morning & was told that when switching to a new mobile phone, you must go to a branch for another mug shot.
Fortunately, Krungsri still have online banking. Account & passport number sufficient to reset my password (forgotten it as I hadn't logged in for over 3 years). I'm also going to transfer most of the funds in there to TTB & leave a nominal amount - Krungsri's loss not mine.
Seemingly, Krungsri have gone from being the easiest to transfer to a new device, to impossible without making an unscheduled trip back to Thailand.