I am not sure if this is Phlyctis or another 'corticoid basidiomycete'. I think its a fungus rather than a "lichen". Seen occasionally on necrotic houhere (Hoheria populnea) branches on otherwise healthy trees. Exposed surface waxy, white. Inner surface of I assume the same fungus erupting through dead host tissue as white, pustular blobs of mycellium.
Voucher: P.J. de Lange 13351 & T.J.P. de Lange, PDD