Do you have a little clearer image? It is really hard to see plant details.

You might try looking at these sites for things to compare with since I really couldn't see much in the way of details to suggest something:

http://vietherbs.com/
http://ediblyasian.info/recipes/cambodian-common-culinary-herbs-and-spices-
http://www.cambodia-cooking-class.com/herbs.htm

I'm sure google can get you other sites to look at - it's how I got these.

FataMorgana

Thanks Morgana, but I've already looked at those sites and many more, but to no avail. This is the first time I've seen this in the market, too, so I guess it's not one of the more common herbs.

Holy Basil?

I'd not suspect holy basil from what I can see. I've grown holy basil for years and that plant is hairy not smooth as the OP's plant appears to be.

It took me a little bit to find it again, but there is a spice/herb site with names of the "spice" in various different languages. I seem to run across it on occasion looking for other info so it made it tricky to find when looking for it specifically. But my google-fu is strong today. *grin* It seems to have some Khmer names so maybe a browse through the list will help.

FataMorgana

Here is a link that might be useful: Spice list name

Zackey - thanks for the suggestion, but I'm afraid this one isn't one of the more commonly seen.
Morgana - Gernot's Spice Pages - he's one of my heroes! I looked there too (that was my first one) :( I did check out the Khmer list again, as the pronunciation of that language doesn't easily convert to English spelling norms.

I'm going to try a few leads in other communities - Burmese and Vietnamese - before I give up.

Thanks again.

Ah well, I'm sorry we couldn't offer more. If you ever get more of the herb, please take another picture. I'm sure we or the folks at the "name that plant" forum could have offered more with a little more of the plant's details visible. If your camera has a "macro" setting (on my camera indicated by a flower icon), use that. It will allow you to take a close up picture without the fuzziness.

If you do find out what it is, please be sure to come back and let us know!

FataMorgana

ps.....while I can't see much of the plant, I'd guess it to be in the Polygonaceae family. It is a big family so that probably doesn't help that much.

Here is a link that might be useful: Polygonaceae

I've seen something like that in some of the local Asian markets. It looks like some type of mint, but not peppermint. Doesn't smell like a mint, though.

Looks kinda like Yerba buena. Micromeria douglasii. Ricardo b.