There is very little information about Thai family law available to Americans. Although this may be a topic of interest for those who study culture, family life, or law, I am not sure that the average American would have a strong reason to know this information. Another exception would be someone who is traveling to or living in Thailand. For someone with personal connections to this country, it would be very beneficial and even necessary to know the law.
Most Americans do not need to know the Family Law of Thailand. However, if an American is traveling to Thailand, then he should probably familiarize himself with Thai laws and customs. If an American is thinking about marrying someone from Thailand, then that person should learn about Thai Fmaily Law as well.
There's no reason for Americans to learn the Family Law of Thailand unless they are planning on visiting the country. Although it's good to know about other cultures and laws around the world, there's really nothing special about Thailand's laws. The laws do have an interesting history, with the approval of multiple wives (and tiers of wives!), but there's really nothing there that Americans can learn from it.
For the vast majority of Americans, the Family Law of Thailand does not effect their personal life. They are much more likely to encounter a problem with family law in the state where they live in. If a person ends up encountering that law, they can find someone to help them understand it.