Wat Rajathiwas Rajaworavihara ( Wat Raja ) is situated on bank of Chao Phraya River, near Tha Wasukri Pier, Samsen. When he was a monk King Rama IV, resided at this temple. It was there that the Dhammayutika sect was born. It is believed to be an ancient temple built before the Ayutthaya Period, and was originally called Wat Samorrai. King Rama V Believed that the word "Samor" was derived from the Khmer word "Thamor", meaning stone. Therefor the temples name meant Wat Silarai. King Rama IV gave the temple its present name of Wat Rajathiwas vihara. The temple is cool and shady as befitting its history as a forest retreat.

In the Fifth Reign the phra ubosot, which has been constructed in the early Rattanakosin Period, was in poor condition. King Rama V therefor ordered Prince Narissaranuwattiwong to reconstruct the phra ubosot but retain the original walls because of the significance of the building in the history of the Dhammayutika sect. The murals were done using the European fresco technique and depicted the story of Phra Vessandara, the Buddha's tenth reincarnation. Prince Narissaranuwattiwong prepared the drafts and Rigole, an Italian artist who painted the ceiling in the dome of the Ananta Samakhom Throne Hall, executed the frescoes.

The sala karn prian, or sermon hall, situated in the front of the temple is constructed entirely of teak and can accommodate up to 1,000 people. Prince Narissaranuwattiwong modelled it on a hall at Wat Suwannaram in Phetchaburi Province.