Wal-Mart shares have tumbled 2 percent since their earnings pop in mid-February, and the charts are pointing to even more pain for the retail giant.

That's at least according to AlphaShark's Andrew Keene, who believes Wal-Mart could drop to its lows from May 2015, especially as "retail has been very, very weak throughout the last couple of weeks."

On a daily chart of Wal-Mart, Keene said that the retailer's shares are seeing "resistance" at $72. "It has found resistance many times at the $72 level and every time it hit $72, over time it sold off," he said Tuesday on CNBC's "Trading Nation."

This leads Keene to believe Wal-Mart shares could fall to around $65, just slightly below its February lows. This means that Wal-Mart is set for a 7 percent drop in the coming months.





To take advantage of a move down for Wal-Mart, Keene wants to buy the May monthly 67.5-strike puts and sell the May monthly 65-strike puts for a total of 77 cents, expiring May 19. "If Wal-Mart goes to under $65 on May expiration, this spread would be worth $2.50," said Keene. "That's good for 3 ½ times my capital."

Wal-Mart is currently up about 1 percent year to date, dropping off from a high of $72.39 as part of its post-earnings run.

Correction: Keene wants to sell the May monthly 65-strike puts. An earlier version misstated the price.