Changing the frame and annotation style in subplot

Is this what you want?

gmt begin insar_plot png
gmt set MAP_FRAME_TYPE inside
    gmt subplot begin 3x3 -Fs3i -A
    gmt basemap -R0/10/0/10 -c
    gmt basemap -R0/10/0/10 -c -Bwsen
    gmt basemap -R0/10/0/10 -c -Bwsen
    gmt subplot end
gmt end show