Ming invaded and annexed Annam. By any definition that constituted aggression.
Ming pursued an offensive strategy against the Mongols who refused to kowtow to the Ming emperor. Ming reached the peak of their power during the reign of the Yongle emperor. The size of the Ming army was estimated to have been anywhere between 1.5 and 2.5 million soldiers. The Ming were by far the most powerful state in the world at the time. As structural realism would predict, in the the period 1368–1449 Ming initiated 29 conflicts, while the Mongols initiated only 10 in the same period. The Veritable Records of the Ming (Ming Shi Lu) noted that the purpose of the military expedition of 1372 was to “annihilate” the Mongols and “clear the desert forever".
Ming sent their uber powerful fleets of 250 ships and almost 30,000 men to project power across South East Asia and the Indian Ocean and through "shock and awe" forced foreign state into submission, thereby expanding the Confucian tributary system. Zheng He even captured the king of Sri Lanka and had him delivered to China. According to the words of Zheng He himself:
"When we reached the foreign countries, we captured barbarian kings who were disrespectful and resisted Chinese civilization. We exterminated bandit soldiers who looted and plundered recklessly. Because of this, the sea lanes became clear and peaceful, and foreign peoples could pursue their occupations in safety."
Because the Mongol keep raiding Chinese northern town so it is classic offensive is the best defense move As to Ming attacking Sri Lanka just as Pi Sigma said it is now called "freedom of navigation"
As I said knowing little history is dangerous. But here is the gist Did Ming colonize Sri Lanka or not? Answer!
Alakeshvara was hostile to the Chinese presence in Ceylon during the first Ming treasure voyage and so Zheng He decided to leave Ceylon for other destinations.