i have all the other documents but what exactly do i need to do in order to get the wp3 form?

Apply for work permit.

What is often referred to as the WP3 Form is actually the A5 sized receipt you get from Labour when a Work Permit application is sucessfully filed, this is often used in lieu of the Letter of Approval from the Ministry of Labour referred to in the MFA list of requirements.

Here is a link to the MFA list of requirements for a non immigrant category 'B' visa.

http://www.mfa.go.th/main/en/services/123/15388-Non-Immigrant-Visa-%22B%22-(for-Business-and.html

WP3 is actually number of the application form (TT3 - ตท.3 ) used by an employer to apply for a Work Permit on behalf of an employee who has not yet entered Thailand.

Form_tt3.pdf

Form WP 1 (TT1 - ตท.1 ) is used for those who are already in Thailand or whose WPs have expired.

Form_tt1.pdf

Vientiane wants the approval letter. A WP3 is not enough. You should check with the embassy or consulate where you plan on applying for the visa to confirm what they want.