@Frank-Steven **********

I have no idea of post-Covid restrictions, nor about motorcycles.

If you enter Tachileik via Mae Sai, no visa is needed if you stay in Tachileik province.

Yep, this is how I was doing border run pre-covid. You do not need to stay overnight.

An affidavit that you are legally free to marry.

OP documents are in English = he cannot get married.

I got married in Phu Pha Man 3 months ago, in and out in 1 hour. All you need is two witnesses, your wife ID card, and the affidavit. I don't know what "original devolve papers" is. Your affidavit need to be translated in Thai and certified. You cannot get married anywhere in Thailand with English paperwork. I don't know what you are referring to.

@Lê *********

BKK airport is the same, going through this airport trying to get out and back in the same day can be difficult. You said "border run" earlier, so I gave you an answer which doesn't apply here since you are not doing a border run. Please, next time, provide accurate information because it can gets very confusing while trying to help. A border run usually refer to getting out of the country by land, just to do a U-Turn and coming back into Thailand immediately (generally 30min-1h later), depending on how long the process is on the other side.

@Lê *********

Flying out and coming back is not a border run. A border run is going out by land and coming back 30 min later after getting into Cambodia and coming back.

You get a bus to the border, not to Siem Reap. Just look at YT video about border run, you don't seem to have done any research. You get out of Thailand and come back in immediately after entering Cambodia.

She probably meant visa exempt (Vietnam). You do not need to pay expensive price for border run with agent service. Just do a normal border run. Are you vaccinated?