Wat Suwannaram is a large royal temple on Bangkok Noi Canal, built under King Rama I and renovated under King Rama III. Its main draw is the mural painting inside the ordination hall, where scenes of the Buddha's previous lives sit among deities and courtly detail.
The temple fits well into a Thonburi canal trip, especially if you are already visiting the Royal Barge National Museum nearby. It is a quieter stop than Wat Arun, but the art rewards a slow look.