Interesting comments and recommendations on the topic. In viewing the comments and looking at other information sites, it appears that in the USA situation, it depends on the state who gets to keep the ring. Thus, it seems almost a 50/50 situation. It is a condition on a promise, therefore not followed through, the ring is returned... If the fault is with the male, then the woman may keep it.... As for the Thai situation.. that was only a question if the problem would occur here. It is open season in Thailand.
There was an interesting case on the tube for an Engagement ring valued at 70K USD... The judge returned it to the male.
The judge was a female and the court was in California.