Agreed to Andreas, my old passport has written CANCELLED and can't use it anymore except to move my old alive visa to a new one, If I were you, I won't take any risk to confuse Thai Immigration by using two passport any chance. Since it's not Europe, you better go with unique one bro
I have a good one which is located in downtown Bangkok as well as in Phuket. You can get free consultation which you can get to know what you need to perform by your side.
22K is way fair price tho, if you need some professional service for your WP, you will have to pay more than 22K for the completed service, if you need one, I can suggest you.