Take a look at the video, the boy plays his tune perfectly. I guess he's been playing the Xylophone all his life since he seems to keep playing even as he looks around.
A Thai style Xylophone like that is called a 'Ranat'. This one is a Ranat ek, with 22 bar, I learned the basic playing technique as part of school lessons in Thai traditional instruments, but to actually usefully play this, grade 5 and upwards (11+) school children can take lessons in it.
This was another Jatujak sighting, outside Jatujak market at the weekend.