I think Nepal still does not have an online payment system. You had to pay via a specific bank in KTM and applicants had an interview. You should double check before applying. There are some posts about applying there which should be in the threads.
You can come and go as you please with the DTV. Attendance is not monitored. In terms of value for money, you would be better off with a flex schedule which matches your stay. Plenty of schools offer that but I don't know about in Koh Samui.
no that is not the guaranteed way of increasing approval as growing recent rejected agent applications have proven. The majority of approvals are given to applicants who apply themselves.
The ask:thailand community, consisting of multiple Q/A groups with over 100,000 members, powers this platform. It is not an official government resource. Our members actively contribute to this resource, and while we strive for accuracy, we cannot guarantee its complete reliability. Assistance to travelers is provided as a community service.