** Shares of Australia's Austral Gold AGD.AX fall as much as 9.7% to A$0.140, their lowest point since April 13
** Stock has gained 11.5% so far this month, on track for its biggest monthly gain in three months
** The gold miner says Guanaco Mine production expected to be at lower end of CY26 forecast range due to lower-than-forecast production in first quarter
** Says first-quarter sales revenue increased by 43% to $34.1 million
** AGD stock down 12.1%, YTD
(Reporting by Keshav Singh Chundawat in Bengaluru)
((Keshav.singhchundawat@thomsonreuters.com))