Health Land is a very large day spa on Pattaya Naklua (Nua) Road.  It is truly first class, but at reasonable prices.  They have all kinds of massages and treatments available, which you can have in less expensive group room settings, or in individual private rooms with private shower inside.  All of the staff seem to be highly trained and speak at least some English. I like the aromatherapy massage, which is 90 minutes for about 700 baht, about $22.  There is a menu of the various massages and treatments available.  When it's done, they serve a copy of hot healthy tea.  The whole place is very clean all around.

Generally, you don't even need an appointment, you can just show up.  They are open seven days from 9 or 10 am, until 10 pm.  They have other locations in Bangkok and maybe other parts of Thailand too.  They cater to both large groups of tourists arriving in big tour buses, but also individual people.  The prices are at least 50% lower than what you would pay in a first class hotel, and in some cases maybe even cheaper.  It is a beautiful big modern building.  There is a small cafe and gift shop and even a doctor for therapeutic treatments and advice.  

They even sell some kind of ticket book of 10 massages for a lower price, which are transferrable and usable in other locations.  They have a good website for more information and pictures.