It's technical, but there is a principle in the case of a previous ruling, where. if there were new evidence relating to the 1907 French map, Thailand could contest the previous Preah Vihar decision. In the current case, Thailand seems to be asserting its maps as evidence of where the border is located, so it's up to the ICJ to decide which country is in the right. I believe that Thailand could also refuse to engage in the ICJ case, without giving a reason.
If analysis shows that Thailand has a case on reviewing the 1962 ruling, it should insist that its claims be reviewed as well as the current Cambodian claims.