Since long I have this link to a table with fines for traffic violations:

http://www.trafficpolice.go.th/fine.php

But still I don't get what the two right columns want to say.

The column titles are:

อัตราโทษ and อัตราตามข้อ กำหนด

In the respecting columns you find the fines for the described violations.

E.g. in line 52 there is the fine for not wearing a helmet when driving a motorcycle.

The columns say:

ปรับไม่เกิน 500 บาท (obviously: "fine not exceeding 500 Baht", "maximum fine"?)

ปรับ 200 บาท ("fine 200 Baht")

Can someone explain what the two columns mean?

When do I pay 200 Baht (only) and when up to 500 Baht?

You pay 400-500 baht when the cop who stopped you has a car or motorbike payment due.