Travel Agents typically represent Tour operator companies by arranging itinerary, transportation, taking payment and issuing a voucher. Agents are found everywhere there are tourists. Some agents have their own air-conditioned shop and are qualified to process online ticket reservations. However, the majority of Tour & Travel agents operate from a small booth along a sidewalk or the lobby of a Hotel or Guesthouse.
Although tour pricing is generally the same between agents, there is an amount of flexibility so it's worthwhile to visit several and do a bit of bargaining. Don't be shy, bargaining is a common practice in Thailand.