I guess that's a pretty reasonable time span to visit all the worthwhile places of both Bangkok and Pattaya. I will suggest that start your trip from Pattaya. Take a bus to Pattaya as soon as you land in Bangkok. It's a 3-4 hours journey. There stay one night. Visit the beach in the morning and the alcazar show and the night market in the evening. Then come back to Bangkok.There keep one separate day to visit the zoo.and next day-The King's Palace,Silom street and few of the Malls. And maybe on the final day,visit the floating market before heading to the airport.