There IS a form which normaly will be accepted by many imm. offices for a home country insurance. But...I hear/read that that form is difficult to get it signed by your home insurance company. Maybe give it a try ? (See form at my own answer)
, I know this one. They asked this 2 times at Korat imm., signed by my (Thai) girlfriend. The last 3 times when I went for my year extension, they gave it back to me. So not sure who has to fill it in for your friend. Maybe they gave it to your friend 'standard' because many of us have a Thai partner.š¤·āāļø
š. I read it before some imm. offices wanted that income statement legalized. Very strange because it has English language and stamp and signature from the Ambassador (or 'right hand' of him). The confirmation of your marriage every year at your Amphur is quite common.