Can I suggest that once you have found your rooms, you don't book them online. You will pay up to 5 times the price. Thailand is empty right now with tourism at an all time low, so all hotels have rooms. If you stay more than 3 nights, push their price down (by at least 20%).

When I used to visit I stayed with family in BKK (never go to Pattaya at night, so no experience there - King?) and in Chiang Mai I used Lai Thai (do a Google on Lai Thai Chiang Mai and you'll get it). It as a lit pool, covered out door restaurant, is central (on the moat by the wall), has aircon, sat TV, on suites, large beds, tours and bike hire and parking - they will also make a deal (rooms from 400B upwards - all now seem to have aircon, it used to be cheap rooms were fan only).