BANGKOK, Jan 20 (Reuters) - A split in one of the biggest parties of Thailand"s ruling coalition has led to the expulsion of 21 lawmakers, its deputy leader said on Thursday, in a sign of cracks widening in Prayuth Chan-ocha chaotic administration. But Palang Pracharat, the second-largest party in parliament with 100 seats, was still willing to work with the faction, which was expelled for causing party disunity, according to deputy leader Paiboon Nititawan. Faction leader Thammanat Prompao, a former deputy agriculture minister and his group, which has 21 seats, has yet to make clear whether it will continue to back the prime minister. Prayuth, who led a 2014 coup and remained prime minister after an election his critics say was stacked in his favour, has led a crowded 18-party coalition, which currently has 267 seats compared with the opposition bloc"s 208. The retired general has come under fire over his handling of the COVID-19 crisis and slow pace to secure vaccines. Since July 2021 he has been the target of the biggest anti-government protests in years. Analysts say the spat could make it harder for Prayuth to govern in Southeast Asia"s second-biggest economy. Prayuth has ruled out dissolving parliament or a cabinet reshuffle. "This is part of the bargaining game between factions," said political scientist Titipol Phakdeewanich of Ubon Ratchathani University, adding it was likely the coalition would remain intact. Political analyst Sukhum Nualsakul said fissures could result in a ministerial shakeup. "This could lead to a cabinet reshuffle so that the government can function better," he said. "Right now it is like the government is constantly at war with itself."