It's definitely less than clear.
Seems simple:
a person is a resident for Mexican tax purposes when that person establishes a home in Mexico.
Then it's not simple:
If the individual has a home in another country, then the individual is a resident of the country where the individual’s centre of vital interests is located. Under Mexican domestic tax law, a person’s centre of vital interests is considered located in Mexico if ...(ii) Mexico is the primary place of the person's professional activities.
A remote worker's professional activities are happening in both places, (it may be worldwide income but a bureaucrat could make the argument that the activity is happening in Mexico) and in my other comment, "worldwide income" is mentioned. This is the reason I've not followed through on the RT; there's a lot of ambiguity. I don't like ambiguity when it comes to tax obligations.