"...the domestic partner laws would give her something".
Which laws are those?
"...if you are unmarried but living with a Thai partner, your partner may not be entitled to anything at all".
https://www.thaicontracts.com/articles/8-thai-law-isn-t-simple/36-foreigners-and-inheritance-in-thailand.html
"De-facto informal marriages, common-law marriage or Buddhist marriage or any religious marriage ceremony are not recognized as legal marriages under Thai Civil Law and therefore do not create any legal rights, duties, powers, or responsibilities of husband and wife. Only officially registered marriages entered into the government´s marriage register are recognized as legal and valid marriages in Thailand and will create the rights, duties and responsibilities of husband and wife under Thai family laws".
https://www.thaicontracts.com/articles/8-thai-law-isn-t-simple/66-marriage-in-thailand.html#:~:text=De-facto informal marriages%2C common,responsibilities of husband and wife.