The night bike tour is a must do. By night the traffic near the Grand Palace and wat pho decreases substantially . This tour takes advantage of that and also rides along back streets and alleys on both sides of the river taking you to and through many interesting sites, many of which are spectacularly illuminated at night.. The weather is cooler and exhaust fumes are decreased at night as well.
The guide is great. He is fluent in English and very knowledgeable about the city, culture and bikes. He is a very safe rider and the ride is safe. It is not taxing, just a hoot. You do ride down some 4 1/2 foot wide paths along the canals so you must be able to control your bike, it is a slow ride, so this should not be a big conern.The bikes are new mountain bikes in very good condition.
The price is 1200B ($40 US) and includes bike, helmet and water. It starts at 6 pm and lasts 3 to 4 hours and covers 5 to 8 miles I would guess. It is an enjoyable, informative way to get the lay of the land around that area. You should definitely do it!