It may be time to hop off the Amazon (AMZN - Get Report) express train. 

Amazon shares have exploded 70% this year on the back of growing optimism on the e-Commerce's giant's retail position, increasing dominance of Amazon Prime and a successful push into original content. A strong second quarter from the tech beast has only helped to fuel the latest push higher in the stock. 

Amazon's stock now trades at a ridiculous 161 times trailing-twelve month earnings. The Nasdaq 100 trades at about 26 times trailing earnings. 

Miller Tabak strategist Matt Maley is tossing a caution flag onto the field on Amazon. Maley's chief concern: Amazon is absurdly overbought at current levels based on the stock's relative strength index (RSI). 

"We're actually concerned about the most popular stock in the market right now: Amazon," Maley says. Putting this stock on the negative side of the ledger might sound crazy, but there is no question in our minds that Amazon has become VERY, VERY over-bought...and thus its upside potential is going to be some-what limited in our least over the next two months."

Adds Maley, "The weekly RSI chart on Amazon now has a reading of 85.69....which is higher than it was back in January (just before it began an almost 10% correction). In fact, it's higher than we saw at the 2007 top...and it's the highest reading we've seen since January of 1999!!!....Also, it's monthly RSI chart has almost reached 90...89.95 to be exact...which is the highest reading ever on a monthly basis......Finally, we'd also point out that Amazon is now trading at a 135% premium to its 200 week moving average. That's also a record...surpassing the 130% premium it reached back in January."

Get ready for that Amazon top, if Maley's numbers crunching is correct.

This is what Jim Cramer is saying about Amazon shares right now