any experience why http://www.pprottweiler.com which seems like being the only Rott breeder around?

Maybe if you extend your search to include Thai language web-sites you will get more hits?

สุนัขชนิดหนึ่ง = Rottweiler

In my limited experience (I know of two Rottweiler breeders in Thailand) most Thai are not using the internet as a sales platform* but communicate via some of the more common social media web-sites (Hi-5, Pantip as well as FB and Craigslist) where you will find discussion and the offer of puppies, although I have seen many "adverts" where generic puppy pictures have been used.

Clearly those posters have better web-scamming skills than being a good breeder, as you may know a good breed does so for the love of the breed rather than money (if done correctly) however I propose that many Rottweiler breeders in Thailand do so with an eye to profit and are doing so within a limited gene-pool.

Very often IME creators of many web-sites do so as a five-minute wonder and completely fail to maintain them (this is not just a Thai centric problem), so any information offered maybe of limited value, with discontinued contact numbers, email addresses and litters that are long since sold.

You will probably find greater choice and valid information in the Thai Dog Show magazines sold in book stores and 7-11 with the usual contact adverts carried within their pages.

As ever if you seek a local breeder talk to a reputable vets or larger pet shops.

I offer a small collection of copied HTML sites with chunky images when searching for Thai Rottweiler sites to get you started, it all has a very 1990s look and feel!

.

http://www.rottweilersociety.com/1home.html (You want this section.)

http://www.dogilike.com/

http://www.thailandrottweilerclub.com/default.asp?content=home

* (and their SEO skills in Thai let alone English are abysmal)

I have friends who have previously bought from this breeder and are very very happy. http://www.ratchburikennel.com/Contact.html

I know the owner of PPrott for over 10 years. Good breeder, good dogs.
Customer recently bought their pup from them. Great dog, great doggenality, great appearance, and physically sound.