Singapore citizen touring China

I am a Singaporean planning to visit China. I land in Chengdu on the 15th of June. I fly out of Urumqi on the 29th evening (6 pm), which is my Day #15 in China. My flight out of Urumqi is not direct. I have a close to 3 hours layover in Beijing and my flight out of Beijing departs at 0010h on the 30th, which would be Day #16. Do I need a visa? Though I will be physically leaving China on the 30th, I presume I would be clearing immigration at Urumqi on the 29th.