Attending meetings is one thing. Taking employment with a Thai entity is another. Between them sits a narrow third category: Thai law provides a notification procedure for specified urgent, necessary or ad-hoc work, covering defined situations such as conferences, seminars, training, specialist inspections and similar short engagements. Work under that procedure must be completed within a short fixed period.
It exists for genuinely short, defined tasks. It is not a way to begin regular employment while a work permit is pending, and using it that way is a poor idea for you and for the company.
For a business visit, missions generally ask for an invitation from the Thai host setting out who you are meeting, why, and for how long, signed by someone authorised to sign for the host. The wording and the exact items differ from one mission to the next, so take your post's own list as the version that counts.