user-1: The only country I know of that definitely has chess as a compulsory subject on its national curriculum is Armenia. Are there any others? I think Paraguay may be one.
Please take "national curriculum" to mean the curriculum that is legally obligatory to be taught in all state schools. Thus England and Wales have a national curriculum, even though there is no obligation for it to be taught either in private schools (attended by about 7% of children) or by home educators.
Quite a bit of chess is taught in Danish, Swedish, and Hungarian schools, but as far as I am aware (and I may be wrong) it is not actually a compulsory subject in any of those countries. I thought it used to be a compulsory subject in the USSR but couldn't find confirmation.

user4418: According to this article in the UK Telegraph newspaper - Spain says yes to chess as game is made compulsory in schools - written in 2015 by IM Malcolm Pein who runs CSC (Chess in Schools and Community) in England.
There are a number of countries where something like CSC exists but, like CSC in England, it is not part of the school curriculum. Spain is the only country I know of which has made it compulsory.

user-1: In this article in the Majorca Daily Bulletin (2015), the Spanish parliament is described as having unanimously passed a resolution that year to allow regional governments to introduce chess as a compulsory or optional subject in schools. The resolution is similarly described as "non-binding" in the Financial Times.
The first-mentioned article further states that

Armenia became the first country to apply the policy nationwide in
2011. Mexico followed in 2014, as well as parts of China, India and Germany.

The word "parts" here implies that chess is not a compulsory part of the national curriculum in those countries as defined in the question. I have not yet found a fully reliable source for the case of Mexico. So far the only certain case I have identified is Armenia.
A report on the international conference on chess in schools held in Armenia in 2014 quotes FIDE's then president Kirsan Ilyumzhinov as follows:

Recently I was in Mexico. They showed me their national school
curricula [sic] and said that they were going to follow Armenia’s example
and make chess a compulsory subject in schools. The same is true for
Paraguay, Mongolia and Thailand.

Regarding Thailand, I wonder which game is being referred to. International chess is much less played in that country than makruk, also known as Thai chess.

-1: <p>The only country I know of that definitely has chess as a compulsory subject on its national curriculum is Armenia. Are there any others? I think Paraguay may be one.</p>
<p>Please take &quot;national curriculum&quot; to mean <em>the curriculum that is legally obligatory to be taught in all state schools</em>. Thus England and Wales have a national curriculum, even though there is no obligation for it to be taught either in private schools (attended by about 7% of children) or by home educators.</p>
<p>Quite a bit of chess is taught in Danish, Swedish, and Hungarian schools, but as far as I am aware (and I may be wrong) it is not actually a compulsory subject in any of those countries. I thought it used to be a compulsory subject in the USSR but couldn't find confirmation.</p>
 4418: <p>According to this article in the UK Telegraph newspaper - <a href="https://www.telegraph.co.uk/culture/chess/11415450/Spain-says-yes-to-chess-as-game-is-made-compulsory-in-schools.html" rel="nofollow noreferrer">Spain says yes to chess as game is made compulsory in schools</a> - written in 2015 by IM Malcolm Pein who runs CSC (<a href="https://www.chessinschools.co.uk/" rel="nofollow noreferrer">Chess in Schools and Community</a>) in England.</p>
<p>There are a number of countries where something like CSC exists but, like CSC in England, it is not part of the school curriculum. Spain is the only country I know of which has made it compulsory.</p>
 -1: <p>In <a href="https://www.majorcadailybulletin.com/news/local/2015/10/24/42099/spanish-schools-have-introduced-chess-class-boost-maths-learning.html" rel="nofollow noreferrer">this article in the Majorca Daily Bulletin (2015)</a>, the Spanish parliament is described as having unanimously passed a resolution that year to allow regional governments to introduce chess as a compulsory or optional subject in schools. The resolution is similarly described as &quot;non-binding&quot; in the <a href="https://www.ft.com/content/a7686122-524c-11e5-b029-b9d50a74fd14" rel="nofollow noreferrer">Financial Times</a>.</p>
<p>The first-mentioned article further states that</p>
<blockquote>
<p>Armenia became the first country to apply the policy nationwide in
2011. Mexico followed in 2014, as well as parts of China, India and Germany.</p>
</blockquote>
<p>The word &quot;parts&quot; here implies that chess is not a compulsory part of the <em>national</em> curriculum in those countries as defined in the question. I have not yet found a fully reliable source for the case of Mexico. So far the only certain case I have identified is Armenia.</p>
<p>A report on the international conference on chess in schools held in Armenia in 2014 quotes FIDE's then president Kirsan Ilyumzhinov as follows:</p>
<blockquote>
<p>Recently I was in Mexico. They showed me their national school
curricula [sic] and said that they were going to follow Armenia’s example
and make chess a compulsory subject in schools. The same is true for
Paraguay, Mongolia and Thailand.</p>
</blockquote>
<p>Regarding Thailand, I wonder which game is being referred to. International chess is much less played in that country than makruk, also known as Thai chess.</p>
