** Hong Kong-listed shares of Chinese humanoid robot maker UBTech slide more than 30% to HK$61.50

** The drop wipes out ~$1.6 bln in market value of Shenzhen-based co

** Plunge comes after expiry of lock-in period for stakes held by major shareholders

** Co says chairman will extend by a year his lock-in period covering 70.4 million shares

** Adds lock-in issue does not have any "material adverse impact on the operation of the group"

** YTD, stock down 31.5%

(Reporting by Anne Marie Roantree; Editing by Donny Kwok)

((donny.kwok@thomsonreuters.com))