She is getting coached by friends or Facebook. It's a pride thing. Thai people have all heard how much some farangs pay to support a gf. 30 k isn't a real bragging amount either.
We don't have many facts. Your age, salary, what's the probability you will want or can stay in Thailand a lifetime. Her living conditions, proximity to where you live. Have you talked about her moving in. Do you talk enough to know your her only guy. Maybe she doesn't feel your worth playing the long game.
I feel they really feel pressured by friends and social media to see how much the man will support her. To a Thai, support is part of the love equation. Maybe it's the same for Western women but usually less obvious. Just remember there are 1000 others like her.