The thing is, if the husband registers the marriage, the spouse doesn't lose her rights as a wife the day he dies. In practice it may be difficult for her to get immovable assets in the husband's home country, but her rights to pensions are at least protected. In Thailand, individuals cannot set up a trust.
FYI. I don't know how the legal system works in different countries but you may want to look into setting up a trust versus a will in case of death. In the U.S., a trust allows you to bypass probate court and therefore avoid some costs and taxes. I would consult an attorney or do some research online. A trust is a little costlier to set up but may be a savings in the long run.