Your thread got hijacked into irrelevant discussion about merits of NAPA in soil that is no help in dealing with the Thrips youre showing in your photos!!
Only the adults can fly so what youve photographed are probably the early larval forms. Your neighbouring trees in gardens or woodlands could be a source of regular re-infestation so routine treatment of the affected bonsai with insecticidal soap seems a good plan. Which bonsai are affected?