Thais can, of course, be very friendly and kind, it's a big part of their culture and features prominently in their education system, but there is also a big culture of saying nothing and not getting involved in various negative aspects of life in Thailand.
We see many news articles of horrible things happening in Thailand, particularly to vulnerable people, and no one says or does a thing (although they probably gossip about it in private).
It's probably not a great idea to think that Thais are all selfish and let horrible things happen to other people either.
What's most interesting is the fact that the OP ignores the number of Thai people who must have completely ignored this Thai girl unconscious on the floor, and chooses only to focus on the two Thai people that decided to help her. The ones that ignored her don't mean anything, but the ones that helped her indicate how friendly, good natured and nice Thai people are.
Selection bias in action.