Yellow-bellied Prinia is one of the commonest birds ringed in Hong Kong. Unfortunately there is not enough visible on this ring to allow the individual to be identified. The number ends in 8, which could be any of five individuals ringed in 2008, or another bird ringed in a previous year. If you have more photos showing more of the ring, this might help to ID the bird.
Well done for noticing and getting photos of this ringed individual.