I sold my PM9 because I found I was carrying my LCP 95% of the time, I was moving away from 9mm, and I wanted to free up funds for other toys... but in hindsight those three combined were not reason enough to sell it off.
Some day I'll probably replace it with a PM40... most definitely if they round off the front corners of the PM slide and do away with the thick 1911-style slide stop in favor of a simple pin and internal stop (like the LCP) .
The Walther PPS would be my second pick, only because its bigger (but its as thin as the PM9)
My BIL has a Springfield Armory XDS 9mm and it is certainly worthy of consideration. I was pleasantly surprised by the accuracy, reliability and handling of this pistol.
Depending on the size of your hand, but I just bought a FEG PA-63 that is like a thin 9mm but has a full size grip. It is very comfortable to hold and has a great point of aim shooting group. Only down side is it is the 9x18 Makarov ammo limitation and does need a Wolf spring kit to make it a better carry.
Ruger LC9s.
The LC9 is a great gun but with a horrible trigger.
Ruger just redesigned the gun as a striker fed--as opposed to hammer--and the trigger pull is now perfect.
Gun store prices are in the $370-4389 range.
It is now called the LC9S and it is, for me, a soon to be must have.
I'll put in my 2 cents for the kahr cm9. Mine is very reliable but you can only get a two finger grip on it which is ok. It conceals easily. Right now there have been great deals on them. Today only the slightly larger CW9 and the CM 40 are on sale at Palmetto State Armory for $299. Check out their Labor day sale.
I also have a Kahr, but pocket carry mine. If you want the smallest and thinnest, that would most likely be the Rohrbaugh, but is expensive. The new Boberg is also worth a look. More cost effective are the various ones mentioned above
SCCY's Model CPX-2, same for the CPX-1, is 1" thick, just under 6" long and 4 & 1/4" tall if you remove the grip extension on the magazine. The pistol comes with the flat magazine base if you choose to use it vs. the grip extension. It holds 10 + 1 rounds of 9mm and has a life time of the pistol warranty with no questions asked on a warranty claim. Made in the USA and can be had brand new for around $250.00 if you shop around. MSRP is about $319.00. SCCY pays the freight both ways if you should have a repair or warranty issue.
I have no affiliation with SCCY but did have an extremely pleasant experience with their customer service folks. They do have a web site, and there is also an SCCY Forum if you want to do some research.