Upon a quick search, I realized this place has been mentioned here a few times, and I actually had not paid attention to those threads. Until this weekend when the store was brought to my attention, by my wife's colleague who asked her a favour and fetch him a bottle of fish sauce from there. So after a quickie lunch at Hon's in Chinatown we strolled over there. I never would have seen it myself driving by as their frontage and signage are rather inconspicuous. At any rate as soon as we walked in I knew this would be a treasure trove of all things Thai (and possibly Vietnamese, Indonesian, Cambodian, etc). Admittedly I didn't take the time to check out their vast plethora of goods (but visual scans of price tags suggest they're super cheap) as I'm not that well-versed in the cuisines of this region of Asia. Wife bought a few packages of curry pastes, as well as the fish sauce her colleague requested (710ml Ruang Tong brand for < $2). I fancied a package of what looks like puffed rice crackers (sweetened with palm sugar, as told by staff) and munched on them as soon as we exited the store. Yum.
I didn't ask the young couple behind the counter what their nationality is (quite possibly Thai), but did manage to find out they themselves have been there since March 2012, but the store has been there since at least 2002.
Anyway I'm just posting this to make future searches and references easier. I'm sure they'll gain extreme popularity in due time. Here's the storefront (red signage):
And some tidbits from the "Y" site: