Catalysis of the reaction: 9beta-pimara-7,15-diene + 3 O2 + 3 NADPH + 3 H+ = 9beta-pimara-7,15-dien-19-oate + 3 NADP+ + 4 H2O. This is a three-step reaction: (a) 9beta-pimara-7,15-diene + O2 + NADPH + H+ = 9beta-pimara-7,15-dien-19-ol + NADP+ + H2O, (b) 9beta-pimara-7,15-dien-19-ol + O2 + NADPH + H+ = 9neta-pimara-7,15-dien-19-al + NADP+ + 2 H2O, (c) 9beta-pimara-7,15-dien-19-al + O2 + NADPH + H+ = 9beta-pimara-7,15-dien-19-oate + NADP+ + H2O.