What documents do I need to apply for a long-term visa to Thailand as a Chinese working in the Philippines?

The Royal Thai Embassy in Manila requires more documents than other countries. Here is some information replied by the consular when I aaked them via email.

Destination Thailand Visa (DTV)

(Workcation / Thai Soft Power Activities / Spouses and dependents of Primary DTV visa

1. Proof of purpose of visit

Workcation:

a.1 Employment Contract

a.2 Employment Certificate stating your scope of work while working remotely, and the nature/industry of your company/business

Professional portfolio showing your freelancer work

Thai Soft Power: Proof of confirmation to attend the activity or a letter of appointment from a hospital or medical center

Dependent of Primary DTV Holder: Proof of relationship, such as a Marriage Certificate, Birth Certificate, or Certificate of Adoption, and Photocopy of Passport and DTV of Primary Visa Holder

2. Bank Certification / Bank Statements from the last three months (Minimum of 500,000THB or the equivalent per applicant)

Local Bank accounts for those holding Philippine Resident Visas

If applicant will have a sponsor to shoulder all travel expenses: Guarantee Letter from sponsor (with a copy of sponsor's passport, and Bank Certificate or Bank Statements)

If applicant will be applying as Dependent of Primary DTV Holder: Bank Certification or Bank Statements should meet the minimum amount required per applicant (500,000THB minimum for 1 applicant)

Yes. Applying online or via embassy is roughly the same. You choose what works better for you.