Depends on where you stay, Bangkok is hugh, with 10million population, you would have too many things to shoot....
Traditional photographing scenes are the Grand Palace, Sleeping Budda, Jade Budda, Golden Budda, all kinds of temples, Riverside market, downtown skyline, traffic jam, people jam, cute policeman, street beggar, etc.
Shopping wise, if you need air-con, then try MahBoonKong mall, if you can live without air-con, can try the weekend market at Chatujaik (or something like that, forgot the spelling, there is MRT station nearby now.)
Dining wise, get out of the hotel areas, go north to eat with the locals, mind you, some authentic Thai restaurants have no chairs, you sit on the mat and eat.