Calling Monsoon a travelogue is like calling Dante's Divine Comedy a travelogue. Both works track the inner spiritual and psychic journeys of their protagonists. Those inner journeys comprise the plot.
If you think the story is about two isolated gay men, full of longing, who find "romantic" love despite the obstacles heterosexual society has set up for them, you wouldn't be wrong. But you wouldn't be right either. And you're likely to find yourself impatient if not bored while watching this movie. Director Hong Khao shifts his/our attention and for some frustrates our expectations for what the stories of same gender-loving men can be and how those stories can function/ are a reflection and container of all humanity's story.
Isolation: both of these gay men are connected to their "people," dead (Kit is returning to Vietnam to find a place to lay to rest his parents' ashes; Lewis has come to Vietnam to find a place to lay to rest the residue of the PTSD his father inherited as a soldier there), and living (Kit is called "a good son" by his childhood friend/cousin, happily fulfills the role of loving/beloved uncle and shares with his brother the deepening relationship with Lewis, an American of African heritage; Lewis' mother is a manager in his Vietnam based business.)
Gay: both gay men in this story are people of the global majority. That is to say, neither is defined by or through the fictional concept of race, with its idea of the superiority of whiteness above all other races. Often movies about gay men feature people who are racialized as white, as though the definition of gay meant white and homosexual. Kim and Lewis, to the contrary, experience each other directly, without going through or accommodating that white lens.
The antagonists in this story are European colonialism, capitalism, and white body supremacy and how their lingering synergistic effects interfere in the most intimate workings of the lives of descendants formerly colonized (Henry Golding's Kit) and formerly enslaved (Parker Sawyers' Lewis) people. The movie is a lot about the possibility of these two groups seeing each other without going through the lens of whiteness.
If you give the director his given circumstances to tell his story, there is much to enjoy and admire here. And it is groundbreaking.