Banks adjust their exchange rates on a daily basis, in line with international money markets, and usually offer the best rates. Hotels and some shops also offer exchange services usually at less favourable rates.
Banking hours in Thailand are 8.30 am to 3.30 pm Monday to Friday. You will find currency exchanges at all major tourist areas. These are open daily from 9.00am until around 6.30pm, with some staying open until late evening.