Bitcoin is rallying. The digital tokens were priced around $7,400 on Thursday at 5:30 p.m. ET — an increase of more than 10 percent from a month ago, according to Coinbase.

But Arthur Hayes, the bitcoin bull who predicted the cryptocurrency would reach $50,000 by year's end just a few weeks ago, said bitcoin hasn't bottomed yet.

"I don't actually think we've seen the worst," Hayes, co-founder and co-CEO of Bitmex, said Thursday on "Fast Money."

His firm, BitMEX, or Bitcoin Mercantile Exchange, is the largest cryptocurrency trading platform by volume.

Hayes told CNBC that the coin could hit "8,000, 9,000 and maybe just shy of 10,000," before falling again.

"I would like to see us test 5,000 to really see if we put a bottom in," Hayes said.

Bitcoin's rally was good news for digital coin traders who watched the largest cryptocurrency by market cap fall below $6,000 last month. The coin recovered a few days later but is still significantly lower than bitcoin's all-time high of around $19,500 last December.