Can I extend my METV and then make a border run before returning to Thailand or should I apply for a Non-Immigrant O Visa?

I saw this question and answer before but can’t find it sorry.

I have a METV and I’m on my second 60 days (after an original 60 and 30 day extension), the Visa has a valid until date of 5th May 2019, can I have another 30 day extension (due before 11th April) then another 60 days (border run) before 5th May, as I am in UK approx all May, then can automatically return on the same Visa.

Or is it better to get a O Non Immigrant Visa whilst in UK from local Hull consulate. Just to add complications I’m hopefully marrying my Thai girlfriend before I go to UK in May and hopefully taking her with me (if all this admin doesn’t drive me crazy beforehand) 🙏