** Shares of ALS Ltd tumble as much as 12.4% to A$13.090, set for worst day since March 16, 2020 - if current losses hold

** Stock down ~9.8% as of 0020 GMT

** Testing services provider says it expects its underlying net profit after tax for the September half to be down by 5% as compared to PCP

** Says decline in NPAT is due to volume headwinds in its commodities business, especially in the Australian and Latin American markets

** Including day's moves, stock has risen ~5.5% this year

(Reporting by Archishma Iyer)

((Archishma.Iyer@thomsonreuters.com;))