The main prayer hall of Wat Sao Thong-Thong
Between Bahn Vichien and the palace, along Rue De France, Wat Sao Thong-Thong was originally built in King Narai's time as a church for the Christian envoys visiting Siam at the time. The church was later converted to a temple. The Christian chapel is now the temple's main prayer hall, which retains a few traces of its earlier use. Inside the chapel is a large, rather brutish, Buddha image.
The temple is not particularly interesting, but may be worth wandering through if walking between Bahn Vichien and the palace.