that is not generous at all. That is the extreme bare minimum that is legally allowed. Even an increase of 100 baht per day would make a huge difference in this person's life and that amount would probably mean nothing to you. Even then if I were to hire someone I would at least pay 15,000 minimum. A good maid is hard to come by that is loyal. All it takes is just one person just pay them just a little bit more and they'll leave you in a heartbeat.
If they have enough money to hire a maid they have enough money to pay an extra $5,000 baht a month. If she didn't have this job someone else would hire her pretty quickly.
I'm very happy to hear that you're taking care of your maid. It always upsets me how others are happy paying someone 7,000 or $8,000 baht a month and having that person work 6 days a week with no life for themselves and nothing really to support their family on. Just just paying an extra 6,000 baht a month could change the maid's Life and the family they try to take care of. And for most westerners that extra amount is negligible. It's also true what you said. You can have someone working hard for you for very little but the moment someone's offers them a small increase in pay, They will leave you in a second. It's better to pay them well and have that loyalty so they stay with you.
dang, I don't know how you're comfortable paying that low of an amount. You are paying the equivalent of roughly $230 a month to hire someone full-time. I would feel bad doing that. You should increase it to 15,000 baht a month and at least give this person a higher quality lifestyle for themselves and their family. That extra $100 a month isn't going to affect you one bit but would make a world of difference in this person's life.