UDAI SIṄGH, BHĀĪ (d.1843), the last ruler of Kaithal state, was the younger of the two sons of Bhāī Lāl Siṅgh. After the death of Bhāī Lāl Siṅgh his elder son Partāp Siṅgh succeeded him, but died soon after without a male heir. Udai Siṅgh therefore became the next ruler in the line with the approval of the British government, whose supremacy Bhāī Lal Siṅgh had, like the other cis-Sutlej states in 1809, accepted. The highlight of Udai Siṅgh's rule was his munificent patronage of the Sikh classic, Bhāī Santokh Siṅgh's Gurpratāp Surya, more popular as Srī Gur Pratāp Sūraj Granth. Santokh Siṅgh came from Paṭiālā to Kaithal in 1825. Before coming to Kaithal he had already put behind a translation of the Sanskrit classic Amar Kosh and Srī Gurū Nānak Prakāsh, a biography in verse of Gurū Nānak. In Kaithal he wrote his Garb Gañjanī ṭīkā (1829), translation of Vālmīkī Ramāyaṇa (1834) and Ātma Purāṇ (n.d.). A magnum opus Srī Gur Pratāp Sūraj Granth was completed in 1843.

        Bhāī Udai Siṅgh died on 15 March 1843 without a male heir. A part of the state thereafter devolved upon Bhāī Gulāb Siṅgh of Arnaulī, the rest of it escheated to the British.