Thank you for 平安是福 and 胡說之 reply.

I did talk with my ex-boss about using him as my reference when I got lay off, and he agreed.

But it was 1 year ago. I didn't contact him since then as I was focus on taking care of family.

When I gave recuriter my reference, I didn't know that they will check it right away by calling my ex-company front-desk. So I didn't get chance to speak with my ex-boss. Should I write a thank-you letter to my ex-boss? But if I do, he might think I get the offer.