I'm a Filipina but I work in Thailand. I want to know what visa to apply for.

You can apply for an F type for that if it lasts for 6 months. Or you can apply for a student X1 type if it last for more than 6 months.
It is possible for you to apply in Thailand if you have residence permit there. It’s worth a try.
The required documents include your passport and copy of its data page, a recently-taken passport-style photo, residence permit in Thailand, relevant documents required by au pair program and the consular officers. You are advised to contact with the embassy of China to inquire about the detailed information.