Anything from backpacker...
Anything from backpacker oriented spots for Baht100 per night to some of the very best hotels in the world-- the Mandarin and the Oriental -- and hundreds in every price range in-between.
In Bangkok I have stayed at the Tower Inn (about US$35), the Montien on Suriwongse (US$100 or so), the Grand President (about $30), and lately, the Majestic on Sukhumvit Soi 4 (about 1400 Baht for a Superior Double room). The Grand President on Sukhumvit Soi 11 is also a good bet, though more expensive than it has been.
In Pattaya, I do NOT recommend the Cosy Beach Hotel next to the upmarket Royal Cliff. Staff at the Cosy Beach are not at all friendly, and the swarm of flies around the uncovered breakfast buffet is like a scene from X-Files. I've stayed there twice and it hasn't changed--we won't go back there. I now stay at the Natural Park Resort on Jomtien Beach--reasonably priced and nice facilities; across the street from the beach.
In Phuket (Patong Beach area) we stayed at the Baan Nern Sai, on a hill overlooking Patong. A bit removed from nightlife but quite new and friendly owners. Decent restaurant and bungalow-style accommodations. Take their shuttle to Patong Beach or rent a small motorcycle or jeep at the hotel.
Anywhere from 900 Baht per night to about 2000 Baht per night, depending on the season and the type of room you arrange. Good locations near embassy,shopping areas and the nightlife of Patpong, Sukhumvit, Siam Square, Soi Cowboy. Also pretty close to the Chao Phrya River. Most have pools and fitness centers. Baan Nern Sai is new, really clean, well-priced, and has friendly staff and onsite owners. The Majestic is close to the shopping and nightlife of Sukhumvit Road and is a short walk to the Skytrain transit system.