Thailand has established a seperate police department that is dedicated to the well-being of tourists visiting the country. They operate in all the main tourist areas and go by the name of the Tourist Police, using the slogan 'your first friend'.
Should you need to contact the Tourist Police, call 1155 or +66 2 678 6800 and you will be put through to an English speaking operator.
Bangkok International airport (BKK) has a large Tourist Police office in the arrivals area on the 1st Floor. Alternatively, the HQ is at the following address:
TPI Tower, 25/26 Liab Khong Road, New Chan Road, Sathorn
Bangkok also has many regular policemen operating on the streets and can be approached for assistance if required. Although they may not be able to speak English to a high level, they are friendly and will always be wiling to help where possible.