Since at least May 3, a video showing what appears to be a military convoy has been circulated on social media with the claim that it shows the Arakan Army preparing near the Bangladesh-Myanmar border.

See posts shared on Facebook with such claims here (archive), here (archive), and here (archive).
Fact-check
Rumor Scanner Team’s investigation reveals that the circulated video does not show the Arakan Army preparing near the Bangladesh border recently. Rather, this video has been circulated online since at least March as footage depicting tensions along the Ethiopia and Eritrea border.
In this investigation, reverse image searches of several key frames from the video in question led to a video posted on March 26 by an X account named “El Druso” (watch here). When comparing the circulated video with this one, similarities are found. The caption of the X post, written in Spanish, states: “Both Ethiopia and Eritrea are deploying troops along their border amid a land-claim dispute. Ethiopia sees the port city of Assab as a possible target for sea access. Eritrea, on the other hand, is focused on the Tigray region.”

Additionally, several other X and Instagram accounts also posted videos on this topic in March regarding the Ethiopia-Eritrea situation.
Notably, in April, the same video was also circulated in reference to ongoing tensions between India and Pakistan.
In other words, before the claim that the video shows the Arakan Army preparing near the Bangladesh border began circulating, it was already being shared as footage of tensions along the Ethiopia-Eritrea border.
Conclusion
The claim that the video shows the Arakan Army preparing near the Bangladesh-Myanmar border is false.