Look to the evidence. What events occurred in the surrounding Andaman Sea and Gulf of Thailand over the last six decades that were the result of Thailand lacking submarines? None.
The maritime issues that have occurred were related to surface ship activities – pirates, illegal fishing, human trafficking, illegal fuel transport – none of which would have been forestalled by the presence of Thai submarines. These purchased submarines do not add to the security of the nation. But they do add to the exorbitant toys that the Thai military seems obsessed with, in contrast to the critical investment needs of Thai enterprises.