I've been using the Singaporean text by Federal, "New Mathematics Counts," for Matayom 1, and 80% was unusable. It doesn't follow the Thai curriculum, doesn't cover same subjects or at same level.
For next year we need an English text for M1 and M2 that follows the Thai curriculum and at roughly the same level. I thought the Thai textbook was too simple - doing graphs but not showing linear equations on them. Then teaching linear eq. without displaying them on graphs. Showing solid objects and then not measuring volume (in fact, not measuring area on plane objects). I thought that would be covered in P5 or P6 (or 5th grade, say in New York State).
At the end of the semester and year, are your Thai students in MEP and EP going to have to take Thai math tests in Thai language? Mine do at least partially. And they're crappy tests. I mean, the test for end of first semester for Matayom 1 was tough, tougher than the problems I saw in the Thai textbook. Besides, I don't have a decent translation of the Thai curriculum.
It must be nice to have adequate resources and support.