You can also try, by way of a ‘test’ application on the official site. There is a drop-down of countries which should be all those allowed.
You may have to play around - trial by error - to see which lets you progress.
You can either save that one OR delete it, I believe.
I only presume that this way works… if it’s the similar embassy protocol & procedure as it is if applying for a 60-day METV from another country.
I can’t swear by this but I think it’s a good indication. I wouldn’t have thought it’s limited to Laos. I’ve applied from South Korea before (for the 60-day…)… and wanted to know if I could before I went there, from Thailand…