With Krungsri you can update your passport number easily enough, however I later discovered that, just like you I couldn't activate my phone App when I replaced it.
Long story short, it turned out that changing your passport number on the bank's main database does not alter the database used by the mobile apps. I had to sign a request at bank authorizing them to re-download my mobile app data from the main database. It took about 3 hours in total to get my app working again.
New passport coming up in 3 years, but at least I know what to do now.