Here are some details about the Max Thunder exercise that North Korea is complaining about:

An F-22 Raptor stealth fighter lands at a military base in Gwangju, Wednesday, amid Max Thunder, a joint military drill between the Air Forces of South Korea and the U.S. / Yonhap

Max Thunder, which North Korea claims is the cause of its decision to cancel high-level talks with the South, is a joint military drill between the Air Forces of South Korea and the United States.

It has been held every May since 2009, with this year’s drill starting May 11 and continuing for two weeks.

The drills include annual defensive exercises with mock combat, and the number of fighter jets and troops this year is similar to those in years past, with some 100 aircraft from both countries participating, according to the Korean Air Force.

This year, eight of the U.S.’s F-22 Raptor stealth fighters were deployed for the drills for the first time. It is said the Raptor fighters can penetrate North Korea’s radar fence and make surgical strikes against strategic facilities.

But unlike the initial plan, B-52 strategic bombers, one of the U.S.’s strategic assets, will not be deployed, amid ongoing talks about North Korea’s denuclearization. Pyongyang has been sensitive about the bomber which can carry nuclear weapons.  [Korea Times]

You can read more at the link, but this is a fairly low level exercise compared to the Key Resolve and UFG exercises. Plus as the article states this low level exercise was even further downgraded by not including the B-52’s.  So it is pretty clear to me that it is just being used as an excuse by the Kim regime to send a message to the Trump administration to reign in officials bringing up suggestions to discuss forbidden topics such as human rights at the upcoming June 12th summit.