I used a visa agent one time during covid. If I was even able to leave Thailand I knew that I could not return, and they always waited unitil the last minute to announce whether covid extensions would be available. I decided to use an agent since I never knew when I might find myself on overstay. I changed from a non-O Retirement to a 12 month marriage extension. That worked fine until I went to the IO in Phuket 10 months later to renew my visa. The Immigration Officer saw the stamp from upcountry and asked me about that. He told me I would be deported if ever did that again. I had to leave Thailand, return on a tourist visa, applly for a 60 day visa and so on.