you need to have a "person of standing" like village head, mayor, or a professional person like police man, doctor, I get a teacher to sign, they need to have a stamp of thier company. It needs to be done every 24 months, if in doubt call uk.gov there very helpful.
the only thing other things you could try. Checking the app is up to date, go to the play store enter bangkok bank and it will either say "open or update"
Delete the app and reinstall it, this is last worse case option.
If you have a partner install the bangkok bank on thier phone and see if it works
what happens? Does it remain a red image? If so your picture in the system is not being matched to your face, maybe best to go too your local branch and see if they can start again, if you have problems communicating phone the BBank helpline who have good English and let them explain the problem.