* RBB Bancorp posted Q2 net income of USD 10.14 million, down 10.27% from Q1; diluted EPS fell to USD 0.59 from USD 0.66. * Net interest income slipped 1.37% to USD 30.09 million from Q1; net interest margin narrowed 9 basis points to 3.06%. * Noninterest income dropped 28.99% to USD 3.02 million from Q1, reflecting a USD 0.22 million loss on OREO versus a USD 0.89 million gain. * Noninterest expense edged down 1.23% to USD 19.02 million from Q1; efficiency ratio worsened to 57.46% from 55.41%. * Total deposits rose to USD 3.4 billion at June 30, up USD 40.2 million from Dec. 31; nonperforming assets fell to USD 43.58 million.