The new digital arrival card asks for a departure vehicale and a date

Not sure what country your frien passport is from but most Thai embassy’s consulates have a fb page you can message them direct to get the official answer but a few people here have already suggested it’s six months which sounds correct

My experience has been only if your travelling to the country the passport is issued can you travel up to the date of expiry which is what happened to me a year ago .

@Charles ********

look at booking twin room generally they have two double beds

That what I do

@Peter *******

sent you a DM