Hoping to get through BKK and immigration in an hour is a very optimistic wish
Every time I fly there it takes me at least an hour to go through immigration, if not 2 hours. I hate BKK for that... unless you land at weird hours when you're the only plane landing.
But as said by others, LCC are what they are.... not a lot of staff in CS. However, I once forgot my iPad on an AirAsia flight to BKK and the CS on the phone was good and super reactive. They even called me back as promised and I managed to get my iPad back!
Guess you were out of luck. Hope you managed to get your plan B all right.