Updates shares, adds background, details from paragraph 4, adds graphic after paragraph 8

June 18 (Reuters) - Shares of Elon Musk's rockets-to-AI firm SpaceX SPCX.O dropped more than 6% on Thursday, as the post-IPO frenzy that briefly placed it among the top five most valuable companies of the world appeared to fizzle out.

Its shares were last down 6.4% at $179.62, after falling nearly 5% in the last session. Despite the losses, the stock still traded more than 30% above its $135 offering price.

Earlier this week, the market capitalization of SpaceX overtook that of Amazon AMZN.O, momentarily even surpassing that of Microsoft MSFT.O.

If the losses persist, SpaceX's market value of $2.52 trillion would shrink by more than $160 billion on Thursday.

Shares of other U.S. space companies were also down. Rocket Lab RKLB.O and Planet Labs PL.N dropped around 3%, while AST SpaceMobile ASTS.O and Intuitive Machines LUNR.O declined around 7% and 3%, respectively.

SpaceX's bankers are preparing to meet investors as early as next week to discuss a bond offering of at least $20 billion, a source said on Thursday, as the newly public company seeks funding for an ambitious and capital-intensive AI expansion.

The company announced on Tuesday that it would buy Anysphere, the startup behind the popular AI coding agent Cursor, for $60 billion in stocks to boost its presence in the lucrative enterprise AI tools market.

Earlier this year SpaceX had acquired Musk's AI startup xAI in a record-setting deal, unifying the entrepreneur's rocket-and-satellite company with the maker of the Grok chatbot.

The rockets-to-AI company's valuation surged past $2 trillion following its blockbuster Nasdaq debut last week. Its shares soared in their first two days of trading before giving up some gains as investors assessed whether the company's rich valuation can be justified by its costly AI push.