Tesla Inc head Elon Musk has sold another batch of shares, this time worth $3.6 billion, in the luxury electric vehicle manufacturer, a filing with the US Securities and Exchange Commission revealed on Thursday. Over a period of three days ended December 14, Musk sold 22 million shares in Tesla. Following the news, Tesla stock declined around 3% on Wednesday’s regular trading, and is down a further 3.2% in pre-market trading on Nasdaq on Thursday. In the middle of the stake sale, Musk on Tuesday tweeted, “At risk of stating obvious, beware of debt in turbulent macroeconomic conditions, especia…