Bhai Udai Singh (d. 1843), the last ruler ofKaithal state, was the younger of the two sons of Bhai Lal Singh. After the death of Bhai Lal Singh, his elder son Partap Singh succeeded him, but died soon after without a male heir. Udai Singh therefore became the next ruler in the line with the approval of the British government, whose supremacy Bhai Lal Singh had, like the other cisSutlej states in 1809, accepted. The highlight of Udai Singh's rule was his munificent patronage of the Sikh classic, Bhai Santokh Singh's Gurpratap Surya, more popular as Sri Gur Pratap Suraj Granth, Santokh Singh came from Patiala to Kaithal in 1825. Before coming to Kaithal he had already put behind a translation of the Sanskrit classic Amar Kosh and Sri Guru Nanak Prakash, a biography in verse of Guru Nanak. In Kaithal he wrote his Garb Can/am Tika (1829), translation of Valmiki Ramayana (1834) and Atma Puran (n.d.). A magnum opus Sii Gur Pratap Suraj Granth was completed in 1843.
Bhai Udai Singh died on 15 March 1843 without a male heir. A part of the state thereafter devolved upon Bhai Gulab Singh of Arnauli, the rest of it escheated to the British.