Well, not quite....
Treasures of Tartary and Other Heroic Tales, by Robert E. Howard (HC)
Gates of Empire and Other Tales, by Robert E. Howard (HC)
These are the ones in print currently that I'm aware of (in addition to the one you mentioned). As for out of print... there were several of those:
The Sowers of the Thunder
The Road of Azrael
The Lost Valley of Iskander
Three-Bladed Doom
Son of the White Wolf
Swords of Shahrazar
not to mention several Oriental pieces in other collections, such as
The Book of Robert E. Howard,
The Second Book of Robert E. Howard, the
Robert E. Howard Omnibus, etc., etc., etc. And, of course, the two recent books put out by Del Rey:
Del Rey Online | The Best of Robert E. Howard Volume 1 by Robert E. Howard
Del Rey Online | The Best of Robert E. Howard Volume 2 by Robert E. Howard
The same is true with his Westerns, of which there are at least 4 collections currently available (albeit there is a fair amount of duplication when you bring them all together), just as there have been several others now out of print, both humorous and straight....
As for his westerns, I'd agree with "The Vultures of Whapeton", as well as several in
The Last Ride; there are also quite a few good ones in the collection of all the stories he wrote for
Action Stories magazine:
The Complete Action Stories, by Robert E. Howard
You might also be interested in looking at these listings of Howard titles:
Product Search - University of Nebraska Press
HOWARD, Robert E.
I also, however, have a strong liking for his supernatural westerns, which sometimes blend genuine folklore of the region his love of the Southwest, resulting in some very powerful stories....