What is the process for reapplying for an O visa through the Thai embassy in London after it has expired?

The user previously held an O visa based on marriage, which has expired. As a parent to a Thai child, they seek guidance on the reapplication process for the O visa at the Thai embassy in London. Comments suggest contacting the embassy directly via email for the necessary steps, while also advising to gather required documents such as marriage certificates and proof of residency.