Hi as a comparison,
one of the inlaws with a degree gets paid 10 000 baht per month for working in a bank. Another works in carrefour for 7000 baht per month.
The average wage according to the Bangkok post last year was 13 500 baht per month, so as stated, the crews will be willing to work hard for the money on offer from Jetstar.
I am pretty sure that all Thai cabin crew, either working overseas, or employed by an overseas carrier but living in Thailand are making more than the average wage in their country.
A senior Thai Airways 744 captain earns in the region of 300 000 baht per month so unlikely they would leave to join Jetstar.
Rgds.