Australia's Tuas hits over 4-year low after unit gets show cause notice
** Shares of telecom firm Tuas TUA.AX fall as much as 40% to A$1.093, their lowest level since June 2022
** Stock last down 31.7%, on track for worst day since May 18, if trend holds
** Co says Singapore's Infocomm Media Development Authority issues show-cause notice to unit, Simba Telecom, asking why the regulator should not make certain findings against it
** In May, Tuas scrapped a deal to buy a stake in mobile operator M1 through its unit after the Singaporean regulator halted the transaction
** Authorities had said that Simba may have used radio frequency spectrum that was not assigned to it to provide mobile services
** About 21.2 mln shares change hands, 5.9x the 30-day average of 3.6 mln
** Stock down 82.4% YTD