Try Gaviscon advance. Yes, it does not "prevent" reflux, but it is a very good treatment. I always take it at night and just live with mild reflux during the day.
And to be clear, not the green Gaviscon, or the purple dual action. Advance only. It really works the best. It is expensive, but you can find it cheaper on shopee or one of those non branded Thai pharmacies (usually the place where people line up) at around 325 baht.