How can I provide pay slips for a job I haven't started yet while applying for a visa in Thailand?

Currently in Vietnam and applied for remote work. I included the employment agreement and a letter from the company owner. They requested docs about the business (I added the registration and a copy of the website), my duties/employment history (I added that and my CV), but also they requested pay slips for 6 months

I haven't started work yet, which was included in the employment agreement (the start date is next week). Has anyone applied for a job they haven't been working at for six months? How can one sent pay slips if they haven't received any yet?

Thanks!