You’ll find them everywhere. The bike is typical fitted with a 75-150 ccm and in scooter design. If you are Burmese you would probably think such a device can seat 3-4 , but I recommend to limit it to the driver and one passenger.
In the cities the motorbike taxi can progress faster than the car, because it can circumvent the congestion. Some of the drivers offer a helmet you can wear, the ones I’ve seen are similar what in Denmark is used when riding a bike and be sure it’s one size fits all.