While Wat Traimit and its golden Buddha statue attracts a lot of tourists, Wat Mangkon Kamalawat is the most venerated temple for local Thais in Chinatown. It is full of dragons, Chinese goddess statues, and almost always smoky, as thousands of devotees come here to light joss sticks and incense, and pray for good luck in the immediate future. The temple is especially vibrant during the big Thai Chinese holidays, like Chinese New Year and the Vegetarian Festival, when it can even be difficult to come in the entrance, as there are so many people lined up to pay respects.
During the holidays, traditional Chinese opera gets performed out back, something that is well worth attending if you happen to be in Bangkok at this time. The performers spend hours perfecting their makeup and costumes, and then perform traditional songs and skits, with a mostly older audience sitting on makeshift seating out in front. The opera used to be wildly popular here, but has declined in recent years due to the internet and video, and the chances of it continuing in the future are not good.
The temple is accessed from Charoenkrung Road, just opposite the Trok Issaranuphap lane across the street, home to traditional Chinese shops and market goods. Wat Mangkon itself sits back from the main road, in a small square. Just look up for the Chinese lanterns to find it.