Consider buying a 1 day or 3 day pass for the BTS skytrain if you are planning to use the BTS during your stay. It is far more convenient than buying tickets all the time and can save you money.
The one-day pass costs 100 baht and the three-day pass 280 baht. Both are available at all BTS ticket offices as well as from several hotels, tour operators, department stores and souvenir shops.