DK exact answer, but do know-as I currently am trying out every week a (for me, and here in BKK, and not at all in/near Silom) guesthse/HTL-that many such inns direct you to the well known sites as booking or agoda (is now owned by bkg, but was started as a genuine ASEAN site long ago and is thus far better known among Asians)
I am aware that those from US often tend to first reach for other such sites, often these are simply copycats. One can even see when walking in this quite touristy area boards etc that direct people to ¨ our best rates are on these´. Perhaps this helps a little bit-but I am 123% sure that so many Pattayans are also reading this soon and will have a better answer
Also about any place will not put its whole inventory of rooms in 1 site, and also hold out a few for walk-ins or those who stay longer etc.