EDIT SEPTEMBER 22, 2017: It is my understanding that the English branch has moved and that the information here is no longer valid.
There is an English/international branch (not ward) in Phnom Penh. It’s in the middle of the city, about a 10-minute walk from the Royal Palace/National Museum area. The map at maps.lds.org is correct, but the time is not. The English branch meets at 9:00 am (not 10), and the Vietnamese branch meets at I think 1:00 pm (not 8:30), though I’m not positive about that one. I know that they meet after the international branch.
Here is what the building looks like on Google Street View. It does not look like a traditional LDS church (i.e., no steeple or anything). Click it for the larger version.
[Page updated on August 25, 2014]