Be careful to keep your knees in and watch your feet in order to avoid injury. When the road opens up, they may go very fast, including between cars. If you have the misfortune to get a daredevil motorcycle driver, or come across an overly aggressive taxi, it can be a harrowing experience.
It's recommended that you be careful who you choose to be your motorcycle taxi driver. At the motorcycle stands, the leader will often choose a driver. You can have some influence in this. You can also tell them to drive slowly, "by CHA-CHA".
Second to safety, the other main disadvantage of taking motorcycle taxis is you're not shielded from pollution, and if you get behind a smoky bus or car then you could be holding your breath.
If you need to flag down a motorcycle taxi within the middle of a soi or on a main road, you do so the same way as for taxis and buses, turning your palm down and waving them in with your fingers, as shown in our photo of requesting someone's presence. However, if you are close to a motorcycle taxi group, then no motorcycle taxi outside that group will pick you up.