According to Thai civil law, unless the testator was declared by court to be not sound of mind which would void the will, claims that testator was not sound of mind at the moment of making the will, needs proof to void the will (meaning the burden of proof lies with those who claim that the testator was not capable of making a Thai will at the time that will was made). Found it in มาตรา 1704
The misunderstanding comes that you rely upon an English text instead of the actual Thai written law. I rely upon the actual Thai language written law.
1656 precedes 1657, 1658,... but doesn't "govern" or define 1657, ...
There are 5 different types of will
Section 1656 describes the first type of will, commonly known as พินัยกรรมแบบธรรมดา Here the testator can sign or even thumb print a printed will, with 2 witnesses.
Then section 1657 describes the second type of will, commonly known as พินัยกรรมแบบเขียนเองทั้งฉบับ --> this is the handwritten will we're talking about, thimbprint is not allowed. (Wouldn't make sense since this has to be completely handwritten by the testator)
These first 2 wills don't need registering. And the handwritten type (2nd type) doesn't need witnesses either.
Then there are 3 more types :
3.พินัยกรรมทำเป็นเอกสารฝ่ายเมือง --> 1658
4.พินัยกรรมทำเป็นเอกสารลับ --> 1660
5.พินัยกรรมทำด้วยวาจา --> 1663
You can't rely on English versions of the law you find on the internet. The English version is just a "more or less" translation with mistakes.
Aha, I see where the misunderstanding comes from :
You used section 1656, which is for the first type of will, which needs 2 witnesses. This is for a printed will. And furthermore you used an incorrect English text, not original Thai.
Handwritten will is section 1657, which doesn't need witnesses.
I base my comments on the original Thai text regarding the different types of wills described in Thai civil law. The difference between the 5 types are described in sections (มาตรา) 1656 to 1663 as part of the whole set of laws regarding Thai will.
This must be a misunderstanding, there is nothing in the specification of handwritten testament which limits the beneficiaries to legal partner.
There are 5 different types of testament specified in Thai law.
The handwritten type is the second one --> พินัยกรรมแบบเขียนเองทั้งฉบับ and described in ป.พ.พ. มาตรา 1657 : has to be entirely handwritten and properly signed (no thumbprint as signing) by the person and needs a date (day month year).
To read the law Article 1657 go to the source at
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%20law/pang01.htm
Then use the find function of your browser to look for 1657 and it will bring you to the specific Article for handwritten testament.