Can I Convert a 30-Day Visa Exemption to a 90-Day Non-O Visa in Bueng Kan?

That is one SMALL (as in totally tiny) immigration office. I doubt they offer it OR if they do they'd have to send it somewhere to get it approved (extending the under consideration period).

I agree, check with them, if they do it get the hand out that lists EVERY document you need AND also see how long it goes under consideration (the time from when you turn in your application for the 90 day Non-O until it is approved). Most offices require 15 days or more left on your 30 day visa exempt, or 60 day tourist visa entry to do the in country conversion BUT some offices require 21 days or more left on the stamp.

Good Luck, report back once you find out if you will so we all know..

or give them a phone call:

Address: 365, Moo 1, Thai Samak, Tambon Bueng Kan, Amphoe Bueng Kan, Bueng Kan,

Hours:

Closed ⋅ Opens 8:30AM Mon

Phone: 042 491 832

Adrian Hide then I suggest you visit Bueng Kan Immigration and ask for their list of requirements. That way you will know.

Read guidance posted by Tod Daniels in this FB Group as it’s step-by-step.