Bell hops, boat men or anyone else who carries things for you should also be tipped. There are no hard and fast rules for this, but 20 baht per bag is sufficient.
Massage therapists, spa technicians and salon employees should also be tipped 10% or more. In salons or spas where there are multiple people providing services, you should tip each person individually. Hotel spas and salons usually add a 10% service charge so, as in restaurants, ask first.
Most people round up their taxi fare (so, for a 52 baht fare the driver would get 60 baht) and tip additionally for drivers who help with luggage or bags.