** Chinese EV maker Xpeng's HK shares 9868.HK jump 14% to HK$92.25, highest level since March 20

** Set for biggest one-day pct rise since Nov 8, 2024; top pct gainer on Hang Seng Automobile Index .HSAMI, which is up 1.9%

** U.S. shares XPEV.N rose 11.7% on Thursday

** Founder-CEO He Xiaopeng bought 3.1 mln shares at avg HK$80.49 on Aug 20-21, ~HK$250 mln ($32 mln) purchase

** HK shares rose 5% between Aug 20 and Aug 21

** HK-listed rivals rise; Great Wall Motor 2333.HK, Li Auto 2015.HK, BYD 1211.HK, Leapmotor 9863.HK and NIO 9866.HK climb between 0.4% and 7.4%

** Hang Seng Tech Index .HSTECH rises 1.6%, benchmark Hang Seng Index .HSI gains 0.3%

** YTD, Hong Kong shares up 91.1%, U.S. stock up 92.5%

(Reporting by Donny Kwok)

((donny.kwok@thomsonreuters.com))